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Jan
14
comment When $\frac{C(n, k)}{n^{k-1}} > 1$?
Well, for $n=k!+t$ we need to compare $(1+t/k!)\cdot(1-1/(k!+t))(1-2/(k!+t))\ldots(1-(k-1)/(k!+t))$ withs 1. Shouldn't be hard (take logarithm, bound it...) — and at least genesis of $s_k$ is clear.
Jan
13
reviewed Close Show that the function $d(x, y)$ is a metric on the set $\mathbb R^2$ .
Jan
13
reviewed No Action Needed Baby Rudin: Chapter 1, Problem 6{d}. How to complete this proof?
Jan
13
reviewed Close Prove Summation to Some Number $n$
Jan
13
reviewed Approve How to calculate $\lim \limits_{x \to 0}{\frac{\sqrt{1 + x + x^2} - 1}{x}}$?
Jan
13
reviewed Close $\lim_{n \to \infty}\sqrt{2+\sqrt{2+\sqrt{2}+\sqrt{2}}}$
Jan
13
comment Summation with Binomial Coefficients, $\sum (-1)^k \binom{m_1}{k} \binom{m_2}{k} $
cf. math.stackexchange.com/q/858250
Jan
13
comment Solve easy sums with Binomial Coefficient
possible duplicate of Understanding a combinatorial relation.
Jan
13
reviewed Close power e irrational number
Jan
13
reviewed Close Maths problem on distance
Jan
13
reviewed Close Prove the following inequality without using differentiation
Jan
13
reviewed Leave Open If such $1+4\sin{10^\circ}=a+b\sin{c^\circ}$ How find this integer $a,b$
Jan
13
comment Summation with Binomial Coefficients, $\sum (-1)^k \binom{m_1}{k} \binom{m_2}{k} $
related: $\sum(-1)^k\binom mk^2$
Jan
13
revised Summation with Binomial Coefficients, $\sum (-1)^k \binom{m_1}{k} \binom{m_2}{k} $
more descriptive title
Jan
12
comment Groups with no nontrivial topology
(Re: «I am quite interested in how the problem changes if G is infinite or finite.») That's easy to answer: changes from completely trivial (finite) to very hard problem that stayed open for almost 40 years (infinite).
Jan
12
comment Groups with no nontrivial topology
@ MO: mathoverflow.net/questions/165783/…
Jan
12
reviewed Close Find a polynomial of degree 3 with rational coefficients, given remainders mod two quadratics
Jan
12
reviewed Close Find all invariant subspace of $A$
Jan
12
reviewed Close limit of the function $x \to 1$
Jan
12
reviewed Close Convention for dummy variables