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Search: id:A056074
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| A056074 |
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Number of 3-element ordered antichain covers of an unlabeled n-element set. |
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+0
4
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| 2, 17, 71, 212, 518, 1106, 2142, 3852, 6534, 10571, 16445, 24752, 36218, 51716, 72284, 99144, 133722, 177669, 232883, 301532, 386078, 489302, 614330, 764660, 944190, 1157247, 1408617, 1703576
(list; graph; listen)
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OFFSET
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3,1
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REFERENCES
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V. Jovovic and G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, Diskretnaya Matematika, 11 (1999), no. 4, 127-138 (translated in Discrete Mathematics and Applications, 9, (1999), no. 6)
V. Jovovic, G. Kilibarda, On enumeration of the class of all monotone Boolean functions, in preparation.
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LINKS
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K. S. Brown, Dedekind's problem
Eric Weisstein's World of Mathematics, Antichain covers"
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FORMULA
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a(n)=C(n + 6, 6) - 6*C(n + 4, 4) + 6*C(n + 3, 3) + 3*C(n + 2, 2) - 6*C(n + 1, 1) + 2*C(n, 0).
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CROSSREFS
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Cf. A056046 for 3-antichain (unordered) covers of a labeled n-set, A047707. See also A056090, A056093.
Sequence in context: A034721 A107815 A042803 this_sequence A054568 A060352 A002523
Adjacent sequences: A056071 A056072 A056073 this_sequence A056075 A056076 A056077
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KEYWORD
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nonn,nice,easy
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AUTHOR
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Vladeta Jovovic, Goran Kilibarda (vladeta(AT)Eunet.yu), Jul 26 2000
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