Formula for the number of partitions of 2N elements
96086
Double Factorial: Number of possibilities to partition a set of $2n$ items into $n$ pairs
79984
Partition of ${1, 2, ... , n}$ into subsets with equal sums.
66842
Number of $n^2\times n^2$ permutation matrices with a 1 in each $n\times n$ subgrid
132133
Number of elements of a finite field
74730
Combinatorial Proof of ${{n}\choose{k}} {{k}\choose{j}} = {{n}\choose{j}} {{n-j}\choose{k-j}}$
115209
Elementary formula for permutations?
47592
Integer partitions in all orderings
92968
how many element of order 2 and 5 are there
15000
Show that number of elements in $(Z/nZ)^*$ is $\phi (n)$
23093
Proof of recursion formula for Stirling number of the second kind
26343
Number of certain (0,1)-matrices, Stanley's Enumerative Combinatorics
24146
Number of ways to partition a rectangle into n sub-rectangles
72591
Find a bijection to prove a fact about integer partitions
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
18881
Number of elements of order $7$ in a group
44214
The number of subsets of a set of cardinality $n$
88628
Proving the total number of subsets of S is equal to $2^n$