A255516 a(n) = A239839(n)/n! where A239839(n) is the number of ordered pairs of permutation functions on n elements where f(f(f(x))) = g(f(g(x))).

1, 1, 2, 3, 7, 13, 29, 53, 126, 258, 602, 1250, 3031, 6703, 16367, 36698, 91731, 214315, 542225, 1284284, 3305371, 8063704, 21017382, 51961767, 137324923, 347282636, 928913378, 2379051372, 6439629060, 16796126329, 45974995358, 121341267340, 335665581851

Offset

0,3

Comments

The fact that A239839(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.

Crossrefs

Cf. A239839.

Sequence in context: A113823 A113843 A199582 * A113884 A070218 A048456

Adjacent sequences: A255513 A255514 A255515 * A255517 A255518 A255519

Keyword

nonn

Author

Paul Boddington, Feb 24 2015

Extensions

a(14)-a(32) from Hiroaki Yamanouchi, Mar 12 2015

Status

approved