Question Number 87884 by M±th+et£s last updated on 06/Apr/20
Answered by mind is power last updated on 06/Apr/20
$$!{k}\:? \\ $$
Commented by M±th+et£s last updated on 06/Apr/20
$${subfactorial} \\ $$
Commented by M±th+et£s last updated on 06/Apr/20
$${also}\:{called}\:{the}\:{derangement}\:{number} \\ $$
Commented by mind is power last updated on 07/Apr/20
$${ok}\:{thanx}\:{i}\:{will}\:{see}\:{definition}\:{i}\:{never}\:{meet}\:{it}\:{befor} \\ $$