A254529 a(n) = n! * (number of mapping patterns on n).

1, 1, 6, 42, 456, 5640, 93600, 1728720, 38344320, 948931200, 26555558400, 817935148800, 27735629644800, 1020596255078400, 40642432179148800, 1737890081351424000, 79498734605402112000, 3871319396080840704000, 200017645344178421760000, 10925549584125028909056000

Offset

0,3

Comments

a(n) is the number of ordered pairs (p, f) such that p f = f p, where p is a permutation and f is an endofunction.

Links

Alois P. Heinz, Table of n, a(n) for n = 0..382

Math Overflow, What is the probability two random maps on n symbols commute?, 2013.

Formula

a(n) = n! * A001372(n). - Joerg Arndt, Feb 01 2015

Crossrefs

Cf. A001372, A053529, A181162.

Sequence in context: A245248 A197712 A306173 * A098461 A284161 A034662

Adjacent sequences: A254526 A254527 A254528 * A254530 A254531 A254532

Keyword

nonn,easy

Author

Martin Fuller, Feb 01 2015

Status

approved