A362650 Number of nonisomorphic unordered triples of involutions on an n-set.

1, 1, 4, 7, 29, 63, 258, 759, 3263, 12250, 56330, 250841, 1235205, 6113154, 31941407, 169613842, 932670975, 5223815423, 30040926830, 175918987173, 1053086891249, 6413469553076, 39818396779256, 251251607202822, 1613056058498375, 10514730684539068

Offset: 0

Author

Andrew Howroyd, May 01 2023

Keywords

• nonn

Comments

Isomorphism is up to permutation of the elements of the n-set.

Examples

			The a(3) = 7 nonisomorphic triples of involutions are:
  {(), (), ()},
  {(), (), (23)},
  {(), (23), (23)},
  {(), (23), (12)},
  {(23), (23), (23)},
  {(23), (23), (12)},
  {(23), (12), (13)}.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..50

Crossrefs

Column k=3 of A362648.

Cf. A362646, A362649.