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A057965
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Triangle T(n,k) of number of minimal 4-covers of a labeled n-set that cover k points of that set uniquely (k=4,..,n).
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4
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1, 55, 10, 1815, 660, 65, 46585, 25410, 5005, 350, 1024870, 745360, 220220, 30800, 1701, 20292426, 18447660, 7267260, 1524600, 168399, 7770, 372027810, 405848520, 199849650, 55902000, 9261945, 854700, 34105, 6430766430
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 4,2
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COMMENTS
| Row sums give A016111.
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LINKS
| Eric Weisstein's World of Mathematics, Minimal cover
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FORMULA
| Number of minimal m-covers of a labeled n-set that cover k points of that set uniquely is C(n, k)*S(k, m)*(2^m-m-1)^(n-k), where S(k, m) are Stirling numbers of the second kind.
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EXAMPLE
| [1], [55, 10], [1815, 660, 65], [46585, 25410, 5005, 350], ...; there are 1815 minimal 4-covers of a labeled 6-set that cover 4 points of that set uniquely.
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CROSSREFS
| Cf. A035347, A057669, A057963, A057964, A057966, A057967(unlabeled case), A057968.
Sequence in context: A151635 A159732 A174946 * A083516 A203907 A178509
Adjacent sequences: A057962 A057963 A057964 * A057966 A057967 A057968
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KEYWORD
| easy,nonn,tabl
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Oct 17 2000
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