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A362645
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Number of nonisomorphic unordered pairs of permutations of an n-set.
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6
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1, 1, 3, 8, 28, 96, 495, 2919, 22024, 190585, 1876379, 20445393, 244087497, 3161870309, 44155439841, 661065427709, 10561205779056, 179324080365257, 3224650449785570, 61218223893369204, 1223523447160284480, 25679025453032962924, 564657001202726478315
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OFFSET
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0,3
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COMMENTS
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Isomorphism is up to permutation of the elements of the n-set.
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LINKS
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EXAMPLE
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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)}.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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