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A005745
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Number of n-covers of a 3-set.
(Formerly M4156)
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3
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1, 6, 23, 65, 156, 336, 664, 1229, 2159, 3629, 5877, 9221, 14070, 20951, 30530, 43634, 61283, 84725, 115461, 155294, 206368, 271210, 352784, 454550, 580509, 735280, 924163, 1153207, 1429292, 1760218, 2154776, 2622859, 3175555, 3825247
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n)=A002727(n)-A002623(n).
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REFERENCES
| R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Vladeta Jovovic, Binary matrices up to row and column permutations
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FORMULA
| G.f.: -x*(x^8-x^7-x^6-2*x^5+2*x^4+x^3-3*x^2-2*x-1)/((x^3-1)^2*(x^2-1)^2*(x-1)^4).
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CROSSREFS
| Cf. A005744, A005746, A005747, A005748, A005771.
Sequence in context: A162267 A009017 A119712 * A045618 A038737 A038797
Adjacent sequences: A005742 A005743 A005744 * A005746 A005747 A005748
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KEYWORD
| easy,nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), May 26 2000
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