Template:AotD

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Permutation

A permutation of a set of $r$ objects is any rearrangement (linear ordering) of the $r$ objects. There are $r!$ (the factorial of $r$) permutations of a set with $r$ distinct objects.

One can also consider permutations of infinite sets. In this case, a permutation of a set $S$ is simply a bijection between $S$ and... [more]