A362764 Number of nonisomorphic 2-sets of permutations of an n-set.

0, 1, 5, 23, 89, 484, 2904, 22002, 190555, 1876337, 20445337, 244087420, 3161870208, 44155439706, 661065427533, 10561205778825, 179324080364960, 3224650449785185, 61218223893368714, 1223523447160283853, 25679025453032962132, 564657001202726477313

Offset: 1

Author

Andrew Howroyd, May 03 2023

Keywords

• nonn

Comments

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

Examples

			The a(3)=5 sets with permutations shown in cycle notation are:
  {(1)(2)(3), (1)(23)},
  {(1)(2)(3), (123)},
  {(1)(23), (12)(3)},
  {(1)(23), (123)},
  {(123), (132)}.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..50

Crossrefs

Column k=2 of A362763.

Cf. A000041, A362645, A362765.

Formula

a(n) = A362645(n) - A000041(n).