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Jun
10
reviewed Close Limit of an increasing function
Jun
10
reviewed Leave Open Equilibrium in difference equations
Jun
9
answered Solving recurrence similar to Catalan number recurrence
Jun
5
comment Is there a closed form for $\sum_{n=0}^{+\infty} \frac{1}{\sqrt {n!}}$?
It seems quite unlikely. See mathforum.org/kb/message.jspa?messageID=5628902 or wilmott.com/messageview.cfm?catid=34&threadid=44616 (which can be found by computing the sum numerically and googling the resulting value).
Jun
3
answered Name of the highest power of 2 smaller than or equal to a given number
May
14
comment Prove that using generating function:For any $n ,k\in N$, the number of partitions of $n$ into parts
If you're being asked this, I suspect you've seen the generating-function proof for the case $k = 1$ - that is, that the number of partitions into parts which appear at most 1 time ("partitions into distinct parts") is the same as the number of partitions into parts not divisible by 2 ("partitions into odd parts"). Can you generalize this proof?
May
11
comment Find a linear reccurrence relation where a(n) is the number of subsets of {1,2,3,…,n} not containing three consecutive numbers.
This is a duplicate of math.stackexchange.com/questions/86249/… , although that question wasn't answered so I recommend leaving this one open.
May
7
answered Let $a,b$ be relative integers such that $2a+3b$ is divisible by $11$. Prove that $a^2-5b^2$ is also divisible by $11$.
May
4
reviewed Close Famous Problems the Experts Could not Solve
May
4
reviewed Leave Open What is meant by a “$S$-strictly diagonally dominant matrix” in the book 'Geršgorin and His Circles'
May
4
reviewed Close A nice set of squares.
Apr
30
reviewed Close What are numbers?
Apr
30
reviewed Close Proof verification for proving $\forall n \ge 2, 1 + \frac1{2^2} + \frac1{3^2} + \cdots + \frac1{n^2} < 2 − \frac1n$ by induction
Apr
30
reviewed Leave Open Help with finding range and equation of a position vector (projectile)
Apr
29
reviewed Leave Open how to combine angle rotations along different axes into one rotation along a single vector
Apr
29
reviewed Leave Open Statistics Problems, I don't understand what this means..
Apr
29
answered Collection all cards in a cardgame
Apr
29
comment If $n$ is composite, then $((n-1)!)^2 \equiv 0 \pmod n$
4 is the only counterexample: see e. g. Benoit Cloitre's comment at oeis.org/A046022
Apr
29
reviewed Looks OK Evaluate $\lim _{n\to \infty }\int_1^2\:\frac{x^n}{x^n+1}dx$
Apr
29
reviewed Looks OK Show that there exists an idempotent element such that $Ra=Re$ holds for ring $R$