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 A005745 Number of n-covers of a 3-set. (Formerly M4156) 3
 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; text; internal format)
 OFFSET 1,2 COMMENTS a(n)=A002727(n)-A002623(n). 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). LINKS Vladeta Jovovic, Binary matrices up to row and column permutations 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). CROSSREFS Cf. A005744, A005746, A005747, A005748, A005771. Sequence in context: A119712 A273314 A281424 * A213557 A273386 A045618 Adjacent sequences:  A005742 A005743 A005744 * A005746 A005747 A005748 KEYWORD easy,nonn AUTHOR EXTENSIONS More terms from Vladeta Jovovic, May 26 2000 STATUS approved

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