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A362764
Number of nonisomorphic 2-sets of permutations of an n-set.
3
0, 1, 5, 23, 89, 484, 2904, 22002, 190555, 1876337, 20445337, 244087420, 3161870208, 44155439706, 661065427533, 10561205778825, 179324080364960, 3224650449785185, 61218223893368714, 1223523447160283853, 25679025453032962132, 564657001202726477313
OFFSET
1,3
COMMENTS
Isomorphism is up to permutation of the elements of the n-set.
LINKS
FORMULA
a(n) = A362645(n) - A000041(n).
EXAMPLE
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)}.
CROSSREFS
Column k=2 of A362763.
Sequence in context: A255803 A121329 A246175 * A283224 A178834 A331720
KEYWORD
nonn
AUTHOR
Andrew Howroyd, May 03 2023
STATUS
approved