Explanation of a regular pattern only occuring for prime numbersVisualized group tables for $mathbb{Z}$ and...

Why didn't Tom Riddle take the presence of Fawkes and the Sorting Hat as more of a threat?

What is the difference between rolling more dice versus fewer dice?

Explanation of a regular pattern only occuring for prime numbers

What happens when the wearer of a Shield of Missile Attraction is behind total cover?

How does Leonard in "Memento" remember reading and writing?

Why is it that Bernie Sanders is always called a "socialist"?

How do you voice extended chords?

Can 5 Aarakocra PCs summon an Air Elemental?

What will happen if I transfer large sums of money into my bank account from a pre-paid debit card or gift card?

What is the difference between "...", '...', $'...', and $"..." quotes?

Plausible reason for gold-digging ant

A Missing Symbol for This Logo

Utilizing a Right and Left Outer Joins in same SELECT

What will happen if Parliament votes "no" on each of the Brexit-related votes to be held on the 12th, 13th and 14th of March?

How can I play a serial killer in a party of good PCs?

Why did the villain in the first Men in Black movie care about Earth's Cockroaches?

How do you funnel food off a cutting board?

Current across a wire with zero potential difference

Has any human ever had the choice to leave Earth permanently?

Visualize manifold specified by equalities

Non-Cancer terminal illness that can affect young (age 10-13) girls?

Why would space fleets be aligned?

Play Zip, Zap, Zop

A starship is travelling at 0.9c and collides with a small rock. Will it leave a clean hole through, or will more happen?



Explanation of a regular pattern only occuring for prime numbers


Visualized group tables for $mathbb{Z}$ and $mathbb{Z}/nmathbb{Z}$Why do some Fibonacci numbers appear in an approximation for $e^{pisqrt{163}}$?Symmetry and trivial solutions to Pell equationsFinding Divisibility of Sequence of Numbers Generated RecursivelyPalindromic Numbers - Pattern “inside” Prime Numbers?Improving clarity and argumentation with hard-to-describe combinatorial proofVisualizing and understanding the roots of $f(z) = z^2 - e^{ivarphi}$Another color scheme for 3D visualizations of complex functionsVisualizing quadratic residues and their structureVisualized group tables for $mathbb{Z}$ and $mathbb{Z}/nmathbb{Z}$Strangely but closely related parametrized curves













5












$begingroup$


Consider multiplication group tables modulo $n$ with entries $k_{ij} = (icdot j) % n$ visualized according to these principles:





  • Colors are assigned to numbers $0 leq k leq n$ from




    • $color{black}{textsf{black}}$ for $k=0$ over


    • $color{red}{textsf{red}}$ for $k=lfloor n/4rfloor$ and


    • $color{silver}{textsf{white}}$ for $k=lfloor n/2rfloor$ and


    • $color{blue}{textsf{blue}}$ for $k=lfloor 3n/4rfloor$ back to


    • $color{black}{textsf{black}}$ for $k = n$





  • Sizes are assigned to numbers $0 leq k leq n$ by




    • $textsf{1.5}$ if $k=lfloor n/4rfloor$ or $lfloor 3n/4rfloor$


    • $textsf{1.0}$ otherwise




  • Positions are shifted by $(n/2,n/2)$ modulo $n$ to bring $(0,0)$ to the center of the table.



Visualized this way, you will occasionally find (for some $n$) highly regular multiplication group tables like these (with $n=12,20,28,44,52,68$):



enter image description here



My question is:




Why do these patterns occur exactly when $n = 4p$ with a prime number $p$?






Find here some examples for $n neq 4p$, e.g. $n=61, 62, 63, 64$:



enter image description here





Here for some other prime numbers: $n = 4cdot 31 = 124$ and $n = 4cdot 37 = 148$:



enter image description here





One may observe that for $n = 4m$ and $x,y = m$ or $x,y = 3m$ the "size 1.5" dots are systematically separated by $0$ (= black) and $n/2$ (= white) dots:



enter image description here





For the sake of completeness: the multiplication group table modulo $8 = 4cdot 2$ (which also qualifies, but not so obviously):



enter image description here










share|cite|improve this question











$endgroup$








  • 3




    $begingroup$
    What do they look like when $n$ is not $4$ times a prime?
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    Could you include an example of a not so regular table?
    $endgroup$
    – Servaes
    2 hours ago










  • $begingroup$
    To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    @RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
    $endgroup$
    – Hans Stricker
    2 hours ago


















5












$begingroup$


Consider multiplication group tables modulo $n$ with entries $k_{ij} = (icdot j) % n$ visualized according to these principles:





  • Colors are assigned to numbers $0 leq k leq n$ from




    • $color{black}{textsf{black}}$ for $k=0$ over


    • $color{red}{textsf{red}}$ for $k=lfloor n/4rfloor$ and


    • $color{silver}{textsf{white}}$ for $k=lfloor n/2rfloor$ and


    • $color{blue}{textsf{blue}}$ for $k=lfloor 3n/4rfloor$ back to


    • $color{black}{textsf{black}}$ for $k = n$





  • Sizes are assigned to numbers $0 leq k leq n$ by




    • $textsf{1.5}$ if $k=lfloor n/4rfloor$ or $lfloor 3n/4rfloor$


    • $textsf{1.0}$ otherwise




  • Positions are shifted by $(n/2,n/2)$ modulo $n$ to bring $(0,0)$ to the center of the table.



Visualized this way, you will occasionally find (for some $n$) highly regular multiplication group tables like these (with $n=12,20,28,44,52,68$):



enter image description here



My question is:




Why do these patterns occur exactly when $n = 4p$ with a prime number $p$?






Find here some examples for $n neq 4p$, e.g. $n=61, 62, 63, 64$:



enter image description here





Here for some other prime numbers: $n = 4cdot 31 = 124$ and $n = 4cdot 37 = 148$:



enter image description here





One may observe that for $n = 4m$ and $x,y = m$ or $x,y = 3m$ the "size 1.5" dots are systematically separated by $0$ (= black) and $n/2$ (= white) dots:



enter image description here





For the sake of completeness: the multiplication group table modulo $8 = 4cdot 2$ (which also qualifies, but not so obviously):



enter image description here










share|cite|improve this question











$endgroup$








  • 3




    $begingroup$
    What do they look like when $n$ is not $4$ times a prime?
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    Could you include an example of a not so regular table?
    $endgroup$
    – Servaes
    2 hours ago










  • $begingroup$
    To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    @RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
    $endgroup$
    – Hans Stricker
    2 hours ago
















5












5








5


3



$begingroup$


Consider multiplication group tables modulo $n$ with entries $k_{ij} = (icdot j) % n$ visualized according to these principles:





  • Colors are assigned to numbers $0 leq k leq n$ from




    • $color{black}{textsf{black}}$ for $k=0$ over


    • $color{red}{textsf{red}}$ for $k=lfloor n/4rfloor$ and


    • $color{silver}{textsf{white}}$ for $k=lfloor n/2rfloor$ and


    • $color{blue}{textsf{blue}}$ for $k=lfloor 3n/4rfloor$ back to


    • $color{black}{textsf{black}}$ for $k = n$





  • Sizes are assigned to numbers $0 leq k leq n$ by




    • $textsf{1.5}$ if $k=lfloor n/4rfloor$ or $lfloor 3n/4rfloor$


    • $textsf{1.0}$ otherwise




  • Positions are shifted by $(n/2,n/2)$ modulo $n$ to bring $(0,0)$ to the center of the table.



Visualized this way, you will occasionally find (for some $n$) highly regular multiplication group tables like these (with $n=12,20,28,44,52,68$):



enter image description here



My question is:




Why do these patterns occur exactly when $n = 4p$ with a prime number $p$?






Find here some examples for $n neq 4p$, e.g. $n=61, 62, 63, 64$:



enter image description here





Here for some other prime numbers: $n = 4cdot 31 = 124$ and $n = 4cdot 37 = 148$:



enter image description here





One may observe that for $n = 4m$ and $x,y = m$ or $x,y = 3m$ the "size 1.5" dots are systematically separated by $0$ (= black) and $n/2$ (= white) dots:



enter image description here





For the sake of completeness: the multiplication group table modulo $8 = 4cdot 2$ (which also qualifies, but not so obviously):



enter image description here










share|cite|improve this question











$endgroup$




Consider multiplication group tables modulo $n$ with entries $k_{ij} = (icdot j) % n$ visualized according to these principles:





  • Colors are assigned to numbers $0 leq k leq n$ from




    • $color{black}{textsf{black}}$ for $k=0$ over


    • $color{red}{textsf{red}}$ for $k=lfloor n/4rfloor$ and


    • $color{silver}{textsf{white}}$ for $k=lfloor n/2rfloor$ and


    • $color{blue}{textsf{blue}}$ for $k=lfloor 3n/4rfloor$ back to


    • $color{black}{textsf{black}}$ for $k = n$





  • Sizes are assigned to numbers $0 leq k leq n$ by




    • $textsf{1.5}$ if $k=lfloor n/4rfloor$ or $lfloor 3n/4rfloor$


    • $textsf{1.0}$ otherwise




  • Positions are shifted by $(n/2,n/2)$ modulo $n$ to bring $(0,0)$ to the center of the table.



Visualized this way, you will occasionally find (for some $n$) highly regular multiplication group tables like these (with $n=12,20,28,44,52,68$):



enter image description here



My question is:




Why do these patterns occur exactly when $n = 4p$ with a prime number $p$?






Find here some examples for $n neq 4p$, e.g. $n=61, 62, 63, 64$:



enter image description here





Here for some other prime numbers: $n = 4cdot 31 = 124$ and $n = 4cdot 37 = 148$:



enter image description here





One may observe that for $n = 4m$ and $x,y = m$ or $x,y = 3m$ the "size 1.5" dots are systematically separated by $0$ (= black) and $n/2$ (= white) dots:



enter image description here





For the sake of completeness: the multiplication group table modulo $8 = 4cdot 2$ (which also qualifies, but not so obviously):



enter image description here







group-theory number-theory visualization






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited 26 mins ago







Hans Stricker

















asked 2 hours ago









Hans StrickerHans Stricker

6,34443991




6,34443991








  • 3




    $begingroup$
    What do they look like when $n$ is not $4$ times a prime?
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    Could you include an example of a not so regular table?
    $endgroup$
    – Servaes
    2 hours ago










  • $begingroup$
    To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    @RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
    $endgroup$
    – Hans Stricker
    2 hours ago
















  • 3




    $begingroup$
    What do they look like when $n$ is not $4$ times a prime?
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    Could you include an example of a not so regular table?
    $endgroup$
    – Servaes
    2 hours ago










  • $begingroup$
    To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
    $endgroup$
    – Robert Israel
    2 hours ago










  • $begingroup$
    @RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
    $endgroup$
    – Hans Stricker
    2 hours ago










3




3




$begingroup$
What do they look like when $n$ is not $4$ times a prime?
$endgroup$
– Robert Israel
2 hours ago




$begingroup$
What do they look like when $n$ is not $4$ times a prime?
$endgroup$
– Robert Israel
2 hours ago












$begingroup$
Could you include an example of a not so regular table?
$endgroup$
– Servaes
2 hours ago




$begingroup$
Could you include an example of a not so regular table?
$endgroup$
– Servaes
2 hours ago












$begingroup$
To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
$endgroup$
– Robert Israel
2 hours ago




$begingroup$
To me the $nne 4p$ examples look just about as regular as the $n=4p$ ones, with the exception of the locations of the "size $1.5$" dots.
$endgroup$
– Robert Israel
2 hours ago












$begingroup$
@RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
$endgroup$
– Hans Stricker
2 hours ago






$begingroup$
@RobertIsrael: To me, too. My question is just about the "size 1.5" dots.
$endgroup$
– Hans Stricker
2 hours ago












2 Answers
2






active

oldest

votes


















4












$begingroup$

If $n=4p$, then for $xy equiv p$ or $3p$ mod $n$ you need $p$ to divide $x$ or $y$ but $2$ to divide neither: thus the "size $1.5$" dots are all on the lines $x = p$, $x = 3p$, $y = p$ and $y = 3p$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Where and how does the primeness of $p$ come into play?
    $endgroup$
    – Hans Stricker
    1 hour ago



















1












$begingroup$

To elaborate a bit on Robert Israels fine answer, first note that:
$$
begin{align}
xy&equiv n/4\
xy&equiv 3n/4
end{align}
$$

implies that $n$ must be divisible by $4$. Hence we only have such situations when $n=4q$ for some $q$. This is true whether $q$ is prime or not. So let us consider $n=4q$ a bit further. Then we look at:
$$
begin{align}
xy&equiv q\
xy&equiv 3q
end{align}
$$

which can be summarized as:
$$
xy=q(2m+1)
$$

for some $m$. This actually reveals why $n=64=4cdot 16$ also appears to somewhat work. Here $q=16$ so any solutions to $xy=16(2m+1)$ will work. We have the lines $x,y=pm2,pm4,pm8,pm16$ with varying density of "size 1.5" points.



When $q$ is prime, the picture becomes simpler since all solutions to $xy=q(2m+1)$ have to lie on one of the four lines $x=pm q,y=pm q$.





I am still a bit unsure of what happens for numbers that are not of the form $n=4q$. One thing is that $xyequivlfloor n/4rfloor$ implies $(n-x)y,x(n-y)equivlceil 3n/4rceil$ so this breaks the symmetry from the cases $n=4q$ to some extend. This breaks parts of the patterns constituting the horizontal and vertical lines.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
    $endgroup$
    – Hans Stricker
    23 mins ago










  • $begingroup$
    @HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
    $endgroup$
    – String
    20 mins ago












  • $begingroup$
    @HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
    $endgroup$
    – String
    16 mins ago










  • $begingroup$
    Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
    $endgroup$
    – Hans Stricker
    11 mins ago








  • 1




    $begingroup$
    @HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
    $endgroup$
    – String
    6 mins ago











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3128053%2fexplanation-of-a-regular-pattern-only-occuring-for-prime-numbers%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









4












$begingroup$

If $n=4p$, then for $xy equiv p$ or $3p$ mod $n$ you need $p$ to divide $x$ or $y$ but $2$ to divide neither: thus the "size $1.5$" dots are all on the lines $x = p$, $x = 3p$, $y = p$ and $y = 3p$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Where and how does the primeness of $p$ come into play?
    $endgroup$
    – Hans Stricker
    1 hour ago
















4












$begingroup$

If $n=4p$, then for $xy equiv p$ or $3p$ mod $n$ you need $p$ to divide $x$ or $y$ but $2$ to divide neither: thus the "size $1.5$" dots are all on the lines $x = p$, $x = 3p$, $y = p$ and $y = 3p$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Where and how does the primeness of $p$ come into play?
    $endgroup$
    – Hans Stricker
    1 hour ago














4












4








4





$begingroup$

If $n=4p$, then for $xy equiv p$ or $3p$ mod $n$ you need $p$ to divide $x$ or $y$ but $2$ to divide neither: thus the "size $1.5$" dots are all on the lines $x = p$, $x = 3p$, $y = p$ and $y = 3p$.






share|cite|improve this answer









$endgroup$



If $n=4p$, then for $xy equiv p$ or $3p$ mod $n$ you need $p$ to divide $x$ or $y$ but $2$ to divide neither: thus the "size $1.5$" dots are all on the lines $x = p$, $x = 3p$, $y = p$ and $y = 3p$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered 2 hours ago









Robert IsraelRobert Israel

325k23214468




325k23214468












  • $begingroup$
    Where and how does the primeness of $p$ come into play?
    $endgroup$
    – Hans Stricker
    1 hour ago


















  • $begingroup$
    Where and how does the primeness of $p$ come into play?
    $endgroup$
    – Hans Stricker
    1 hour ago
















$begingroup$
Where and how does the primeness of $p$ come into play?
$endgroup$
– Hans Stricker
1 hour ago




$begingroup$
Where and how does the primeness of $p$ come into play?
$endgroup$
– Hans Stricker
1 hour ago











1












$begingroup$

To elaborate a bit on Robert Israels fine answer, first note that:
$$
begin{align}
xy&equiv n/4\
xy&equiv 3n/4
end{align}
$$

implies that $n$ must be divisible by $4$. Hence we only have such situations when $n=4q$ for some $q$. This is true whether $q$ is prime or not. So let us consider $n=4q$ a bit further. Then we look at:
$$
begin{align}
xy&equiv q\
xy&equiv 3q
end{align}
$$

which can be summarized as:
$$
xy=q(2m+1)
$$

for some $m$. This actually reveals why $n=64=4cdot 16$ also appears to somewhat work. Here $q=16$ so any solutions to $xy=16(2m+1)$ will work. We have the lines $x,y=pm2,pm4,pm8,pm16$ with varying density of "size 1.5" points.



When $q$ is prime, the picture becomes simpler since all solutions to $xy=q(2m+1)$ have to lie on one of the four lines $x=pm q,y=pm q$.





I am still a bit unsure of what happens for numbers that are not of the form $n=4q$. One thing is that $xyequivlfloor n/4rfloor$ implies $(n-x)y,x(n-y)equivlceil 3n/4rceil$ so this breaks the symmetry from the cases $n=4q$ to some extend. This breaks parts of the patterns constituting the horizontal and vertical lines.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
    $endgroup$
    – Hans Stricker
    23 mins ago










  • $begingroup$
    @HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
    $endgroup$
    – String
    20 mins ago












  • $begingroup$
    @HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
    $endgroup$
    – String
    16 mins ago










  • $begingroup$
    Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
    $endgroup$
    – Hans Stricker
    11 mins ago








  • 1




    $begingroup$
    @HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
    $endgroup$
    – String
    6 mins ago
















1












$begingroup$

To elaborate a bit on Robert Israels fine answer, first note that:
$$
begin{align}
xy&equiv n/4\
xy&equiv 3n/4
end{align}
$$

implies that $n$ must be divisible by $4$. Hence we only have such situations when $n=4q$ for some $q$. This is true whether $q$ is prime or not. So let us consider $n=4q$ a bit further. Then we look at:
$$
begin{align}
xy&equiv q\
xy&equiv 3q
end{align}
$$

which can be summarized as:
$$
xy=q(2m+1)
$$

for some $m$. This actually reveals why $n=64=4cdot 16$ also appears to somewhat work. Here $q=16$ so any solutions to $xy=16(2m+1)$ will work. We have the lines $x,y=pm2,pm4,pm8,pm16$ with varying density of "size 1.5" points.



When $q$ is prime, the picture becomes simpler since all solutions to $xy=q(2m+1)$ have to lie on one of the four lines $x=pm q,y=pm q$.





I am still a bit unsure of what happens for numbers that are not of the form $n=4q$. One thing is that $xyequivlfloor n/4rfloor$ implies $(n-x)y,x(n-y)equivlceil 3n/4rceil$ so this breaks the symmetry from the cases $n=4q$ to some extend. This breaks parts of the patterns constituting the horizontal and vertical lines.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
    $endgroup$
    – Hans Stricker
    23 mins ago










  • $begingroup$
    @HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
    $endgroup$
    – String
    20 mins ago












  • $begingroup$
    @HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
    $endgroup$
    – String
    16 mins ago










  • $begingroup$
    Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
    $endgroup$
    – Hans Stricker
    11 mins ago








  • 1




    $begingroup$
    @HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
    $endgroup$
    – String
    6 mins ago














1












1








1





$begingroup$

To elaborate a bit on Robert Israels fine answer, first note that:
$$
begin{align}
xy&equiv n/4\
xy&equiv 3n/4
end{align}
$$

implies that $n$ must be divisible by $4$. Hence we only have such situations when $n=4q$ for some $q$. This is true whether $q$ is prime or not. So let us consider $n=4q$ a bit further. Then we look at:
$$
begin{align}
xy&equiv q\
xy&equiv 3q
end{align}
$$

which can be summarized as:
$$
xy=q(2m+1)
$$

for some $m$. This actually reveals why $n=64=4cdot 16$ also appears to somewhat work. Here $q=16$ so any solutions to $xy=16(2m+1)$ will work. We have the lines $x,y=pm2,pm4,pm8,pm16$ with varying density of "size 1.5" points.



When $q$ is prime, the picture becomes simpler since all solutions to $xy=q(2m+1)$ have to lie on one of the four lines $x=pm q,y=pm q$.





I am still a bit unsure of what happens for numbers that are not of the form $n=4q$. One thing is that $xyequivlfloor n/4rfloor$ implies $(n-x)y,x(n-y)equivlceil 3n/4rceil$ so this breaks the symmetry from the cases $n=4q$ to some extend. This breaks parts of the patterns constituting the horizontal and vertical lines.






share|cite|improve this answer











$endgroup$



To elaborate a bit on Robert Israels fine answer, first note that:
$$
begin{align}
xy&equiv n/4\
xy&equiv 3n/4
end{align}
$$

implies that $n$ must be divisible by $4$. Hence we only have such situations when $n=4q$ for some $q$. This is true whether $q$ is prime or not. So let us consider $n=4q$ a bit further. Then we look at:
$$
begin{align}
xy&equiv q\
xy&equiv 3q
end{align}
$$

which can be summarized as:
$$
xy=q(2m+1)
$$

for some $m$. This actually reveals why $n=64=4cdot 16$ also appears to somewhat work. Here $q=16$ so any solutions to $xy=16(2m+1)$ will work. We have the lines $x,y=pm2,pm4,pm8,pm16$ with varying density of "size 1.5" points.



When $q$ is prime, the picture becomes simpler since all solutions to $xy=q(2m+1)$ have to lie on one of the four lines $x=pm q,y=pm q$.





I am still a bit unsure of what happens for numbers that are not of the form $n=4q$. One thing is that $xyequivlfloor n/4rfloor$ implies $(n-x)y,x(n-y)equivlceil 3n/4rceil$ so this breaks the symmetry from the cases $n=4q$ to some extend. This breaks parts of the patterns constituting the horizontal and vertical lines.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 1 min ago

























answered 29 mins ago









StringString

13.8k32756




13.8k32756












  • $begingroup$
    Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
    $endgroup$
    – Hans Stricker
    23 mins ago










  • $begingroup$
    @HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
    $endgroup$
    – String
    20 mins ago












  • $begingroup$
    @HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
    $endgroup$
    – String
    16 mins ago










  • $begingroup$
    Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
    $endgroup$
    – Hans Stricker
    11 mins ago








  • 1




    $begingroup$
    @HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
    $endgroup$
    – String
    6 mins ago


















  • $begingroup$
    Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
    $endgroup$
    – Hans Stricker
    23 mins ago










  • $begingroup$
    @HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
    $endgroup$
    – String
    20 mins ago












  • $begingroup$
    @HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
    $endgroup$
    – String
    16 mins ago










  • $begingroup$
    Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
    $endgroup$
    – Hans Stricker
    11 mins ago








  • 1




    $begingroup$
    @HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
    $endgroup$
    – String
    6 mins ago
















$begingroup$
Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
$endgroup$
– Hans Stricker
23 mins ago




$begingroup$
Thanks for this answer! May I help with specific visualizations? Where and why are you "still a bit unsure"?
$endgroup$
– Hans Stricker
23 mins ago












$begingroup$
@HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
$endgroup$
– String
20 mins ago






$begingroup$
@HansStricker: Thank you. Well, it is just that the "patternless" cases, ie. no horizontal or vertical lines, behave in a more chaotic-seeming manner regarding the 1.5 dots.
$endgroup$
– String
20 mins ago














$begingroup$
@HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
$endgroup$
– String
16 mins ago




$begingroup$
@HansStricker: If you are able to draw more clear conclusions for those "chaotic" cases where $nneq 4q$ or to visualize them in order to see different principles at play, please let me know. I think the floor function is what throws in the "chaos" in the first place :o)
$endgroup$
– String
16 mins ago












$begingroup$
Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
$endgroup$
– Hans Stricker
11 mins ago






$begingroup$
Ah! I didn't suspect the floor function. How would you suggest to get rid of it? Any other suggestions to "draw more clear conclusions" in order to "see different principles at play"? (Thanks anyway for your suggestions.)
$endgroup$
– Hans Stricker
11 mins ago






1




1




$begingroup$
@HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
$endgroup$
– String
6 mins ago




$begingroup$
@HansStricker: I would put my money on Robert Israel or the like for deeper insights. I merely took his work and explained some helpful details, I guess :o) I regret my comment about the floor function. The main players are the factorizations themselves. The floor function merely compensates for the unsuccesful division of $n$. Any rounding technique would be equally chaotic, I think.
$endgroup$
– String
6 mins ago


















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3128053%2fexplanation-of-a-regular-pattern-only-occuring-for-prime-numbers%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Parapolítica Índice Antecedentes El escándalo Proceso judicial Consecuencias Véase...

How to remove border from elements in the last row?Targeting flex items on the last rowHow to vertically wrap...

Tecnologías entrañables Índice Antecedentes Desarrollo Tecnologías Entrañables en la...