A239836 Number of ordered pairs of permutation functions f,g on a size n set where f(g(g(x))) = g(f(f(x))).

1, 1, 2, 6, 48, 360, 2880, 20160, 241920, 3265920, 47174400, 678585600, 12933043200, 193037644800, 3661488230400, 74537438976000, 1736591560704000, 36991492521984000

Offset

0,3

Links

Table of n, a(n) for n=0..17.

Formula

a(n) = A255525(n) * n!.

Crossrefs

Cf. A000012, A000085, A000142, A088311, A053529, A001044, A239779, A255525.

Sequence in context: A281027 A271961 A362798 * A052593 A358065 A052586

Adjacent sequences: A239833 A239834 A239835 * A239837 A239838 A239839

Keyword

nonn,more

Author

Chad Brewbaker, Mar 27 2014

Extensions

a(8)-a(9) from Giovanni Resta, Mar 27 2014

a(10)-a(17) from Max Alekseyev, Jan 29 2025

Status

approved