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Search: id:A055130
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| A055130 |
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Triangle T(n,k) of numbers of k-covers of an unlabeled n-set, k=1..2^n-1. |
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+0
1
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| 1, 1, 2, 1, 1, 4, 9, 10, 6, 3, 1, 1, 7, 29, 87, 181, 287, 364, 365, 290, 187, 97, 39, 13, 4, 1, 1, 10, 72, 417, 1973, 7745, 25830, 74017, 183420, 395311, 744495, 1229807, 1787135, 2289925, 2591162, 2591163, 2289929, 1787148, 1229846, 744592, 395498
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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[1],[1,2,1],[1,4,9,10,6,3,1],...; There are 9 3-covers of an unlabeled 3-set: {{1,2},{2,3},{1,2,3}}, {{1,2},{2,3},{1,3}}, {{1,2},{3},{1,2,3}}, {{1},{1,2},{1,2,3}}, {{1,2},{2,3},{3}}, {{1,2},{2},{2,3}}, {{1},{2},{1,2,3}}, {{1},{2},{1,3}} and {{1},{2},{3}}.
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CROSSREFS
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Row sums give A055621.
Sequence in context: A107388 A107389 A111569 this_sequence A051292 A094424 A083677
Adjacent sequences: A055127 A055128 A055129 this_sequence A055131 A055132 A055133
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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), Jun 14 2000
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