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Search: id:A005746
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| A005746 |
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Number of n-covers of a 4-set.
(Formerly M4634)
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+0
4
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| 1, 9, 51, 230, 863, 2864, 8609, 23883, 61883, 151214, 350929, 778113, 1656265, 3398229, 6743791, 12983181, 24311044, 44377016, 79124478, 138048553, 236050954, 396137624, 653286102, 1059923990, 1693594250, 2667568235
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)=A006148(n)-A002727(n)
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REFERENCES
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R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
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LINKS
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Vladeta Jovovic, Binary matrices up to row and column permutations
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FORMULA
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G.f.: - x*(x^27 - 2*x^26 + x^25 - 3*x^23 + 4*x^22 - 2*x^21 + 4*x^20 + 3*x^19 - 5*x^18 - 5*x^17 - 19*x^16 - 24*x^15 - 31*x^14 - 86*x^13 - 123*x^12 - 205*x^11 - 248*x^10 - 253*x^9 - 242*x^8 - 201*x^7 - 127*x^6 - 92*x^5 - 35*x^4 - 26*x^3 - 9*x^2 - 3*x - 1)/((x^4 - 1)^3*(x^3 - 1)^4*(x^2 - 1)^3*(x - 1)^6).
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CROSSREFS
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Cf. A005744, A005745, A005747, A005748, A005771.
Sequence in context: A140389 A055900 A054549 this_sequence A061178 A097789 A080624
Adjacent sequences: A005743 A005744 A005745 this_sequence A005747 A005748 A005749
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KEYWORD
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easy,nonn
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AUTHOR
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njas, Simon Plouffe (plouffe(AT)math.uqam.ca)
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EXTENSIONS
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More terms and g.f. from Vladeta Jovovic (vladeta(AT)Eunet.yu), May 26 2000
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