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Search: id:A056046
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| A056046 |
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Number of 3-antichain covers of a labeled n-set. |
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+0
7
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| 0, 0, 0, 2, 56, 790, 8380, 76482, 638736, 5043950, 38390660, 285007162, 2079779416, 14995363110, 107204473740, 761823557042, 5390550296096, 38026057186270, 267656481977620, 1881017836414122, 13204444871932776
(list; graph; listen)
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OFFSET
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0,4
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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)=(1/6)*(7^n-6*5^n+6*4^n+3*3^n-6*2^n+2).
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EXAMPLE
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There are 2 3-antichain covers of a labeled 3-set: {{1},{2},{3}}, {{1,2},{1,3},{2,3}}.
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CROSSREFS
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Cf. A047707.
Sequence in context: A134501 A037176 A045819 this_sequence A080313 A080268 A009555
Adjacent sequences: A056043 A056044 A056045 this_sequence A056047 A056048 A056049
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic, Goran Kilibarda (vladeta(AT)Eunet.yu), Jul 25 2000
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