A255515 1/n! times the number of ordered pairs of permutation functions f,g on n elements where f(f(x)) = g(f(g(x))).

1, 1, 1, 2, 4, 5, 9, 17, 26, 46, 87, 137, 246, 474, 791, 1420, 2783, 4839, 8806, 17361, 31252, 57613, 114497, 211496, 395637, 791597, 1495016, 2834242, 5710510, 10986325, 21101677, 42796060, 83674582, 162695172, 332141014, 658589710, 1295551257, 2661881254

Offset

0,4

Comments

The fact that A239837(n) is a multiple of n! follows from a general result in group theory due to Solomon.

Links

Hiroaki Yamanouchi, Table of n, a(n) for n = 0..60

L. Solomon, The solutions of equations in groups, Arch. Math., V.20. no.3, (1969) 241-247.

Formula

a(n) = A239837(n)/n!.

Crossrefs

Cf. A239837.

Sequence in context: A226447 A073151 A279786 * A067298 A077389 A122991

Adjacent sequences: A255512 A255513 A255514 * A255516 A255517 A255518

Keyword

nonn

Author

Paul Boddington, Feb 24 2015

Extensions

a(14)-a(37) from Hiroaki Yamanouchi, Mar 12 2015

Status

approved