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

%I A362764 #6 May 03 2023 21:36:36
%S A362764 0,1,5,23,89,484,2904,22002,190555,1876337,20445337,244087420,
%T A362764 3161870208,44155439706,661065427533,10561205778825,179324080364960,
%U A362764 3224650449785185,61218223893368714,1223523447160283853,25679025453032962132,564657001202726477313
%N A362764 Number of nonisomorphic 2-sets of permutations of an n-set.
%C A362764 Isomorphism is up to permutation of the elements of the n-set.
%H A362764 Andrew Howroyd, <a href="/A362764/b362764.txt">Table of n, a(n) for n = 1..50</a>
%F A362764 a(n) = A362645(n) - A000041(n).
%e A362764 The a(3)=5 sets with permutations shown in cycle notation are:
%e A362764   {(1)(2)(3), (1)(23)},
%e A362764   {(1)(2)(3), (123)},
%e A362764   {(1)(23), (12)(3)},
%e A362764   {(1)(23), (123)},
%e A362764   {(123), (132)}.
%Y A362764 Column k=2 of A362763.
%Y A362764 Cf. A000041, A362645, A362765.
%K A362764 nonn
%O A362764 1,3
%A A362764 _Andrew Howroyd_, May 03 2023