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Hippalectryon
  • Member for 9 years, 9 months
  • Last seen more than a month ago
  • France
47 votes
17 answers
17k views

Interview riddle

43 votes
1 answer
1k views

What is that curve that appears when I use $\ln$ on Pascal's triangle?

38 votes
0 answers
3k views

This should be a piece of cake...... right?

35 votes
3 answers
3k views

Why is Banach–Tarski's paradox so interesting?

23 votes
7 answers
5k views

A riddle for 2015

14 votes
3 answers
1k views

Prove that when dividing a square field among three people, one person must own two points more than 1 km apart

11 votes
3 answers
991 views

Determinant of $a_{i,j}=(x_i+y_j)^k$

10 votes
1 answer
513 views

A question from the dreams realm

9 votes
2 answers
526 views

An expression for $U_{h,0}$ given $U_{n,k}=\frac{c^n}{c^n-1}(U_{n-1,k+1})-\frac{1}{c^n-1}(U_{n-1,k})$

9 votes
2 answers
3k views

Multiplying using reciprocal, addition and subtraction

9 votes
4 answers
270 views

Number of digits of the number of digits of the number of digits of $2014^{2014}$

8 votes
1 answer
203 views

Probability of an integer being a prime

7 votes
1 answer
562 views

Approximation of the exponential

7 votes
1 answer
635 views

Accelerating approximations for arccos

6 votes
0 answers
2k views

Derivative of a composition of function - nice proof

6 votes
2 answers
341 views

Riddle : Given an integer power, does any integer to this power start with the power?

6 votes
1 answer
108 views

Determinant of matrix with entries $a_{ij}=e^{a_ib_j}$

6 votes
1 answer
620 views

Approximating the exponential function

5 votes
0 answers
181 views

Folding sheets of paper to measure distances

5 votes
0 answers
320 views

$A$ a ring, ($\exists n\in\mathbb{N},n\geq 2,\ \forall x\in A$, $x^n=x$) $\Rightarrow$ A is commutative?

5 votes
1 answer
169 views

Symmetrical of a triangle's vertexes

5 votes
1 answer
102 views

Basis of the matrices with only non diagonalizable matrices

5 votes
1 answer
1k views

Maximum dimension of a nilpotent vector space

5 votes
1 answer
509 views

Combination of linear functions that give the derivative operator

5 votes
2 answers
73 views

$(u_{2n})$,$(u_{2n+1})$,$(u_{3n+1})$ converge $\underset{???}{\Rightarrow}(u_n)$ converges

5 votes
1 answer
153 views

Simple eigenvalue and eigenvector of $\{\sin(|i-j|x)\}_{1\le i,j\le5}$

4 votes
1 answer
1k views

First order differential equation with non constant coefficients

4 votes
1 answer
313 views

convergence of $u_n=\sqrt{a_1+\sqrt{a_2+\sqrt{\dots+\sqrt{a_n}}}}$

4 votes
1 answer
184 views

Problem on matrices : $\dim E\leq n^2-(n-r)^2-1$

4 votes
1 answer
391 views

$f(AB)=f(A)f(B)$, show that $f$ is or injective or zero

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