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This tag is used if a reference is needed in a paper or textbook on a specific result.
2
votes
Accepted
On a sum involving Euler totient function
I have found a proof of more general formula in the book Postnikov, A. G. Introduction to analytic number theory American Mathematical Society, 1988, (section 4.2). This proof is simple but it has a s …
10
votes
Accepted
Frobenius number for three numbers
Simple algoritm based on continued fractions was proposed by Rödseth, O. J. On a linear Diophantine problem of Frobenius J. Reine Angew. Math., 1978, 301, 171-178
All algorithm are described in Ramre …
4
votes
Frobenius number for three numbers
Rödseth formula for Frobenius numbers is good not only for computation. It allows to find weak asymptotic for Frobenius numbers with three arguments and density function for normalized Frobenius numbe …
20
votes
Conway's lesser-known results
Conway's Soldiers. And an interesting special case Reaching row 5 in Solitaire Army.
5
votes
1
answer
971
views
On a sum involving Euler totient function
Let
$$S_a(N)=\sum_{n\le N}\frac{\varphi(an)}{n^2}.$$
The usual machinery gives an asymptotic formula
$$S_a(N)=\frac1{\zeta(2)}\cdot\frac{a^2}{\varphi_+(a)}\log N+C(a)+O(N^{-1+\varepsilon}a^{1+\varepsi …
9
votes
Is it possible to "get" quaternions without specifically postulating them?
They can be deduced via Dirac Belt Trick, see Understanding Quaternions and the Dirac Belt Trick by Mark Staley. This Trick is also known as Plate Trick.
3
votes
1
answer
233
views
Addition law for elliptic curves of the form $x^2y^2+a(x+y)+b=0$
Did anybody consider addition law for elliptic curves of the form $$x^2y^2+a(x+y)+b=0\,?$$ Does this form have any specific name?
1
vote
Accepted
Addition law for elliptic curves of the form $x^2y^2+a(x+y)+b=0$
It was done by Euler . Here you can see original text and english tranclation. $\smile$
Now it is known as Euler-Chasles correspondence.
1
vote
Growth rate for the average of the entries in the fundamental period of the continued fracti...
Also a partial answer.
Partial quotients in periods of quadratic irrationals satisfy the
Gauss-Kuz’min law (in average over quadratic irrationals with the length $\le N$), see Spin chains and Arnold …
1
vote
Is it possible to approximate irrational by fractions with denominator and numerator odd?
The formula $|\alpha-(2m+1)/(2n+1)|<\epsilon/(2n+1)$ is equivalent to $\|\alpha m+\frac{\alpha-1}{2}\|<\epsilon/2,$ where $\|x\|$ is a distance from $x$ to nearest integer. This problem is covered by …
1
vote
Frequency of digits in powers of $2, 3, 5$ and $7$
It is not an answer but some numercal data for $A_2(N)$. Here digits are ordered according to their frecuences ($2$, $4$ and $6$ look like most frequent):
$$
\begin{array}{rl}
N=1000: & 2, 1, 4, 6, 8, …
3
votes
Last term of repeating continued fraction expansion
This result is classical, but unfortunately many usual textbooks (e.g. Davenport's "The higher arithmetic") don't give a direct refference to the original paper. This theorem belongs to Évariste Galo …
10
votes
Accepted
Counting points on elliptic curves
Corresponding sums of Legendre symbols are know as Jacobsthal sums $$J(u)=\sum_{x\mod p}\left(\frac {x^3+ux}p\right).$$
They are equal to $0$ for prime $p\equiv 3\pmod4$. If $p\equiv 1\pmod4
$, $\le …
11
votes
2
answers
1k
views
Yang–Baxter explanation
What are the most simple examples which can explain the meaning of Yang–Baxter equation? Is there any way to explain this mysterious object to a person who is not a professional in quantum groups? Il …
4
votes
How close do partitions get to perfect squares?
Numerical results give random picture. If it is really the case then usual heuristic arguments confirm your conjecture.
ListPlot[Table[FractionalPart[Sqrt[PartitionsP[i]]], {i, 1, 5000}]]
Distance …