Simplification of a Combinatoric problem (n k)^2
6366
Combinatorial proof of summation of $\sum\limits_{k = 0}^n {n \choose k}^2= {2n \choose n}$
75804
Is this permutation-sum problem NP-complete?
34334
Combinatorics Problem with symbols and spaces
5801
Combinatorial proof help
111954
Computing the cardinality of a combinatorial set
97314
Counting nearly-sorted permutations
1627
Cartesian product of an arbitrary number of sets
71534
Combinatorial explanation for why $n^2 = {n \choose 2} + {n+1 \choose 2}$
85023
Permutation of n objects with restriction of adjacent pairs
41205
Help me solve a combinatorial problem
88356
Number of options to distribute $N$ different balls to $K$ numbered cells
93748
Alternative to Subsets to generate k-combinations
24588
Proving the combinatorial identity ${n \choose k} = {n-2\choose k-2} + 2{n-2\choose k-1} + {n-2\choose k}$
143573
Problem (1.8) A Path to Combinatorics Solution Verification.
76635
Proof through combinatorial argument
85104
Counting train stops using combinatorics
21000
Calculating $\sum_{k=1}^nk(k!)$ combinatorially