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Fedor Petrov

Saint-Petersburg, Russian Federation

http://www.pdmi.ras.ru/eng/perso/petrov.php

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69
integral of a "sin-omial" coefficients=binomial
mathoverflow.net

59
Examples of notably long or difficult proofs that only improve upon existing results by a small amount
mathoverflow.net

54
Most elementary proof showing that exponential growth wins against polynomial growth
mathoverflow.net

51
The number $\pi$ and summation by $SL(2,\mathbb Z)$
mathoverflow.net

43
Prove that expression is integer
mathoverflow.net

40
Important formulas in combinatorics
mathoverflow.net

40
A curious sin-integral
mathoverflow.net

39
Does there exist a graph with maximum degree 8, chromatic number 8, clique number 6?
mathoverflow.net

39
Nonequivalent definitions in Mathematics
mathoverflow.net

37
How to prove $e^x\left|\int_x^{x+1}\sin(e^t) \,\mathrm d t\right|\le 1.4$?
mathoverflow.net

36
Alternative proofs sought after for a certain identity
mathoverflow.net

34
Examples of common false beliefs in mathematics
mathoverflow.net

33
How to prove positivity of determinant for these matrices?
mathoverflow.net

30
An equality involving roots of unity which holds most of the times, but not always
mathoverflow.net

30
A conjectural trigonometric identity
mathoverflow.net

30
What is the simplest proof that the density of primes goes to zero?
mathoverflow.net

29
Sum over permutations is 1
mathoverflow.net

29
Special rational numbers that appear as answers to natural questions
mathoverflow.net

28
Simultaneous Diophantine approximation of $\sqrt{2}$, $\sqrt{2+\sqrt{3}}$ and $\sqrt{2- \sqrt{3}}$
mathoverflow.net

28
A combinatorial identity
mathoverflow.net

28
What is the value of this double sum in closed form?
mathoverflow.net

26
What is the minimal size of a partial order that is universal for all partial orders of size n?
mathoverflow.net

26
An equality about sin function?
mathoverflow.net

25
Is it possible to create a polynomial $p(x)$ with this relation between $p(0)$ and $p(c)$?
mathoverflow.net

25
Combinatorial identity: $\sum_{i,j \ge 0} \binom{i+j}{i}^2 \binom{(a-i)+(b-j)}{a-i}^2=\frac{1}{2} \binom{(2a+1)+(2b+1)}{2a+1}$
mathoverflow.net

25
How to prove that $a + b + 4 \sqrt{1 + a^{2} + b^{2}} \leq 4 \sqrt{a^{2} + b^{2}} + \sqrt{1+b^{2}} + \sqrt{1+a^{2}} + 2 $ for all $a, b > 0$?
mathoverflow.net

25
Does $8a+5$ ever divide $b^2+8$?
math.stackexchange.com

24
Partitioning a Rectangle into Congruent Isosceles Triangles
mathoverflow.net

24
Examples of eventual counterexamples
mathoverflow.net

23
What is the shortest polynomial divisible by $(x-1)(y-1)(x^2y-1)$
mathoverflow.net

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