Simple combinatorics formula
101889
What is an intuitive explanation of the combinations formula?
1139
Combinatorial proof of $\sum_{j=0}^{k} \binom{n}{j} = \sum_{j=0}^k \binom{n-1-j}{k-j}2^j$
33104
Combinatorial Proof with Summation Identity
137973
What is the formula for Combination with repetition?
43076
Chess tournament combinatorics
20221
Combinatorics - Removing Double Counted Cases
108747
A simple permutation question - discrete math
44484
Combinatorial identity $i{n \choose i } =n {n-1 \choose i - 1}$
15349
Combinatorics riddle: keys and a safe
98313
Number of possible permutations of n1 1's, n2 2's, n3 3's, n4 4's such that no two adjacent elements are same?
71591
Formula for completing the square?
26343
Number of certain (0,1)-matrices, Stanley's Enumerative Combinatorics
96585
Sums and permutation
30575
How to precalculate valid number of combinations instead of using while loop?
70282
Help finding a combinatorial proof of $k {n \choose k } = n {n - 1 \choose k -1}$
60416
Finding a permutation, and number of, from powers of the permutation
123967
Proof of a generating functions formula