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 A362645 Number of nonisomorphic unordered pairs of permutations of an n-set. 6
 1, 1, 3, 8, 28, 96, 495, 2919, 22024, 190585, 1876379, 20445393, 244087497, 3161870309, 44155439841, 661065427709, 10561205779056, 179324080365257, 3224650449785570, 61218223893369204, 1223523447160284480, 25679025453032962924, 564657001202726478315 (list; graph; refs; listen; history; text; internal format)
 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 A148866 A327015 Adjacent sequences: A362642 A362643 A362644 * A362646 A362647 A362648 KEYWORD nonn AUTHOR Andrew Howroyd, May 01 2023 STATUS approved

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Last modified August 9 11:22 EDT 2024. Contains 375042 sequences. (Running on oeis4.)