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Search: id:A055538
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| A055538 |
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Number of asymmetric types of (3,n)-hypergraphs without isolated nodes, under action of symmetric group S_3; asymmetric n-covers of an unlabeled 3-set. |
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+0
1
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| 4, 20, 65, 170, 383, 779, 1470, 2611, 4418, 7182, 11283, 17213, 25601, 37230, 53074, 74327, 102434, 139133, 186501, 246988, 323479, 419344, 538492, 685438, 865376, 1084236, 1348777, 1666664, 2046551, 2498179, 3032482, 3661673, 4399374
(list; graph; listen)
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OFFSET
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3,1
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COMMENT
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Cover may include both empty sets and multiple occurrences of a subset.
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FORMULA
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G. f. : (1/(1-x)^8-3/(1-x)^4/(1-x^2)^2+2/(1-x)^2/(1-x^3)^2-3/(1-x)^4+3/(1-x)^2/(1-x^2)+6/(1-x)^2-6/(1-x))/6.
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EXAMPLE
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There are 4 asymmetric (3,3)-hypergraphs without isolated nodes: {{1,2},{1,2},{1,3}}, {{1},{1,2},{1,2,3}}, {{1},{1,2},{2,3}}, {{1},{2},{1,3}}.
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CROSSREFS
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Cf. A005745.
Adjacent sequences: A055535 A055536 A055537 this_sequence A055539 A055540 A055541
Sequence in context: A018211 A135507 A131479 this_sequence A123613 A006740 A061981
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Jul 09 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jul 11 2000
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