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Ewan Delanoy

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Top Questions
79 votes

What my dog really hears

code-golf string substitution asked May 9 '17 at 8:07
codegolf.stackexchange.com

46 votes

How can “[” be an operator in the PHP language specification?

php specifications asked Jan 9 '16 at 14:42
stackoverflow.com

32 votes

A circle in the plane contains at most four lattice points?

euclidean-geometry asked Jul 30 '15 at 20:55
math.stackexchange.com

30 votes

Smallest order for finite group that needs many elements to generate it

group-theory finite-groups asked Nov 2 '11 at 13:10
math.stackexchange.com

27 votes

Divisibility property for sequence $a_{n+2}=-2(n-1)(n+3)a_n-(2n+3)a_{n+1}$

sequences-and-series modular-arithmetic recurrence-relations asked Apr 8 '18 at 16:16
math.stackexchange.com

20 votes

Comparing countable models of ZFC

logic set-theory model-theory asked Sep 13 '11 at 4:35
math.stackexchange.com

18 votes

Is $SO_n({\mathbb R})$ a divisible group?

linear-algebra group-theory lie-groups divisible-groups asked Dec 19 '13 at 6:23
math.stackexchange.com

18 votes

Square root of positive definite nonsymmetric matrix

linear-algebra matrices asked Feb 10 '14 at 7:24
math.stackexchange.com

17 votes

Why is $(\sqrt{2}+\sqrt{3})^{2008}$ so close to an integer?

number-theory algebraic-number-theory approximation-theory asked Jun 9 '14 at 19:41
math.stackexchange.com

15 votes

Every endomorphims is a linear combination of how many idempotents in infinite dimensions?

linear-algebra asked Aug 6 '14 at 8:55
math.stackexchange.com

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Top Answers
26
Interesting Olympiad Style Problem about Invariance
math.stackexchange.com

24
Is it possible for an irreducible polynomial with rational coefficients to have three zeros in an arithmetic progression?
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24
Does there exist rational $a,b,c$, such that $\sqrt[3]{1}+\sqrt[3]{2}+\sqrt[3]{4}=\sqrt[3]{a}+\sqrt[3]{b}+\sqrt[3]{c}$
math.stackexchange.com

20
Let $a_{i} \in\mathbb{R}$ ($i=1,2,\dots,n$), and $f(x)=\sum_{i=0}^{n}a_{i}x^i$ such that if $|x|\leqslant 1$, then $|f(x)|\leqslant 1$. Prove that:
math.stackexchange.com

18
How to Prove that the minimum of two exponential random variables is another
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17
Example of two dependent random variables that satisfy $E[f(X)f(Y)]=Ef(X)Ef(Y)$ for every $f$
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15
Prove that $2^n-3$ is squarefree
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14
$f(x)$ with real co-efficient and degree 2011 there is a real number $b$ such that $f(b)=f'(b)$
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12
How to represent Fermat number $F_n$ as a sum of three squares?
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12
what is the sum of this?$\frac12+ \frac13+\frac14+\frac15+\frac16 +\dots\frac{1}{2012}+\frac{1}{2013} $
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11
How to find the eigenvalues and Jordan canonical form of this matrix
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11
Algebra Iranian Olympiad Problem
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10
How does (21) factor into prime ideals in the ring $\mathbb{Z}[\sqrt{-5}]$?
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10
Prove that $g(x)=\frac{\ln(S_n (x))}{\ln(S_{n-1}(x))}$ is increasing in $x$, where $S_{n}(x)=\sum_{m=0}^{n}\frac{x^m}{m!}$
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10
Prove that $\phi(n) \geq \sqrt{n}/2$
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10
How find this determinant $\det(\cos^4{(i-j)})_{n\times n}$
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10
convergence in probability induced by a metric
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10
Find the value of $a+b+c$
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10
Polynomials invariant under the action of $S_m \times S_n$
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10
When is a sum of consecutive squares equal to a square?
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10
Does $2x^2-1=y^5$ have a solution in integers, with $y>1$?
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10
symplectic lie algebra is simple
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10
Integers expressible in the form $x^2 + 3y^2$
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9
The Chinese remainder theorem and distributive lattices
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9
Prove:$A B$ and $B A$ has the same characteristic polynomial.
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9
Galois group of a biquadratic quartic
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9
Dual of a rational convex polyhedral cone
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9
eigenvalues of integral matrices
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9
Real roots of a polynomial of real co-efficients , with the co-efficients of $x^2 , x$ and the constant term all $1$
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9
Determining if a recursively defined sequence converges and finding its limit
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