A362825 Number of ordered triples of involutions on [n] that pairwise commute.

1, 1, 8, 22, 232, 1016, 12496, 73648, 1032032, 7586272, 118141696, 1033672256, 17668427008, 178649596672, 3313667912192, 37898019913216, 756948065453056, 9640771045925888, 205935949714235392, 2885307792776353792, 65568056040976818176

Offset: 0

Author

Andrew Howroyd, May 06 2023

Keywords

• nonn

Comments

Two involutions x,y on [n] commute if x*y = y*x.

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..200

Crossrefs

Column k=3 of A362824.

Cf. A362819.

Programs

PARI

seq(n) = {Vec(serlaplace(exp(x + 7*x^2/2 + 7*x^4/4 + x^8/8 + O(x*x^n))))}

Formula

E.g.f.: exp(x + 7*x^2/2 + 7*x^4/4 + x^8/8).