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

0,3

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

Formula

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

Prog

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

Crossrefs

Column k=3 of A362824.

Cf. A362819.

Sequence in context: A131622 A217275 A183308 * A117613 A215740 A304177

Adjacent sequences: A362822 A362823 A362824 * A362826 A362827 A362828

Keyword

nonn

Author

Andrew Howroyd, May 06 2023

Status

approved