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 A057971 Number of 5 x n binary matrices with 2 unit columns up to row and column permutations. 2
 2, 18, 133, 873, 5182, 27786, 135370, 602454, 2466628, 9358497, 33134431, 110184932, 346141949, 1032550097, 2938104492, 8006865684, 20971632456, 52958252851, 129291697111, 305924724070, 703108665327, 1572722761341 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS A unit column of a binary matrix is a column with only one 1. First differences of a(n) give number of minimal 5 - covers of an unlabeled n - set that cover 7 points of that set uniquely (if offset is 7). LINKS FORMULA Number of 5 x n binary matrices with k unit columns up to row and column permutations is coefficient of x^k in (1/5!)*(Z(S_n; 27 + 5*x, 27 + 5*x^2, ...) + 10*Z(S_n; 13 + 3*x, 27 + 5*x^2, 13 + 3*x^3, 27 + 5*x^4, ...) + 15*Z(S_n; 7 + x, 27 + 5*x^2, 7 + x^3, 27 + 5*x^4, ...) + 20*Z(S_n; 6 + 2*x, 6 + 2*x^2, 27 + 5*x^3, 6 + 2*x^4, 6 + 2*x^5, 27 + 5*x^6, ...) + 20*Z(S_n; 4, 6 + 2*x^2, 13 + 3*x^3, 6 + 2*x^4, 4, 27 + 5*x^6, 4, 6 + 2*x^8, 13 + 3*x^9, 6 + 2*x^10, 4, 27 + 5*x^12, ...) + 30*Z(S_n; 3 + x, 7 + x^2, 3 + x^3, 27 + 5*x^4, 3 + x^5, 7 + x^6, 3 + x^7, 27 + 5*x^8, ...) + 24*Z(S_n; 2, 2, 2, 2, 27 + 5*x^5, 2, 2, 2, 2, 27 + 5*x^10, ...)), where Z(S_n; x_1, x_2, ..., x_n) is cycle index of symmetric group S_n of degree n. G.f.: x^2/120*(15/(1 - x^1)^27 + 70/(1 - x^1)^13/(1 - x^2)^7 + 45/(1 - x^1)^7/(1 - x^2)^10 + 60/(1 - x^1)^6/(1 - x^3)^7 + 20/(1 - x^1)^4/(1 - x^2)^1/(1 - x^3)^3/(1 - x^6)^2 + 30/(1 - x^1)^3/(1 - x^2)^2/(1 - x^4)^5). CROSSREFS Cf. A001752, A056885, A057222, A057223, A057524, A057669, A057963-A057968, A057970-A057972, A057969, A057970, A057972. Sequence in context: A277661 A064447 A043022 * A073512 A005544 A154636 Adjacent sequences:  A057968 A057969 A057970 * A057972 A057973 A057974 KEYWORD nonn AUTHOR Vladeta Jovovic, Oct 21 2000 STATUS approved

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