Combinations and Permutations

• combin(n, k)—Returns the number of subsets of k elements that can be formed from n elements. Each subset is known as a combination, defined as follows:

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• permut(n, k)—Returns the number of ways of ordering n distinct elements taken k at a time. Each ordered arrangement is known as a permutation, defined as follows:

Combinations and permutations are both methods of counting subsets of items, however, internal order is significant in a permutation but not in a combination. The number of combinations is usually denoted by

. The number of permutations is usually denoted by