Combinatorics problem about divisors
134478
Find the highest natural number which is divisible by $30$ and has exactly $30$ different positive divisors.
134921
Find the number of all subsets of $\{1, 2, \ldots,2015\}$ with $n$ elements such that the sum of the elements in the subset is divisible by 5
97947
How can we prove that a binomial coefficient $n\choose m$is divisible by the ratio of $n$ and $\gcd(n,m)$?
12134
divisibility question in abstract algebra over a field
124685
How to show $(mn)!$ is divisible by $(m!)^n$?
14783
A Number Theory problem (GCD)
34334
Combinatorics Problem with symbols and spaces
8458
Combinatorics problem based on Ferrers graph
156383
Proving a combinatorial identity without double counting
98082
Another combinatorics problem: $\sum\limits_{k = 0}^n (-1)^k \binom{2n-k}k2^{2n-2k}=2n+1$
134440
An unexpected application of non-trivial combinatorics
139039
Stars and Bars Combinatorics Problem
146867
Combinatorial Proof Of A Number Theory Theorem--Confusion
71625
Divisibility question
9302
Questions about Divisibility of $2^n$ by $3$
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
27141
Combinatorics identity question