A362645 Number of nonisomorphic unordered pairs of permutations of an n-set.

1, 1, 3, 8, 28, 96, 495, 2919, 22024, 190585, 1876379, 20445393, 244087497, 3161870309, 44155439841, 661065427709, 10561205779056, 179324080365257, 3224650449785570, 61218223893369204, 1223523447160284480, 25679025453032962924, 564657001202726478315

Offset

0,3

Comments

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

Links

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

Example

The a(3)=8 pairs of permutations with permutations shown in cycle notation are:
  {(1)(2)(3), (1)(2)(3)},
  {(1)(2)(3), (1)(23)},
  {(1)(2)(3), (123)},
  {(1)(23), (1)(23)},
  {(1)(23), (12)(3)},
  {(1)(23), (123)},
  {(123), (123)},
  {(123), (132)}.

Crossrefs

Column k=2 of A362644.

Cf. A362649.

Sequence in context: A148864 A148865 A203152 * A026627 A376230 A148866

Adjacent sequences: A362642 A362643 A362644 * A362646 A362647 A362648

Keyword

nonn

Author

Andrew Howroyd, May 01 2023

Status

approved