## Permutations

A permutation is an ordered arrangement of distinct objects in a sequence. Each
unique ordering of objects is called a permutation. For positive integers n
and r with
n ≥ r, the number of permutations of a sequence is defined as:

A permutation is an ordered arrangement of distinct objects in a sequence. Each
unique ordering of objects is called a permutation. For positive integers n
and r with
n ≥ r, the number of permutations of a sequence is defined as: