subfactorial

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English[edit]

English Wikipedia has an article on:
Wikipedia

Etymology[edit]

sub- +‎ factorial

Noun[edit]

subfactorial (plural subfactorials)

  1. (mathematics, combinatorics) The result of deranging a number. In equations, it is usually symbolised by an exclamation mark (!) before the number being deranged (as opposed to factorials, where the exclamation mark occurs after the number).