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 A055780 Number of symmetric types of (3,2n)-hypergraphs under action of complementing group C(3,2). 1
 1, 7, 14, 35, 57, 98, 140, 210, 281, 385, 490, 637, 785, 980, 1176, 1428, 1681, 1995, 2310, 2695, 3081, 3542, 4004, 4550, 5097, 5733, 6370, 7105, 7841, 8680, 9520, 10472, 11425, 12495, 13566, 14763, 15961, 17290, 18620, 20090, 21561, 23177, 24794, 26565 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The first g.f. gives a 0 between each two terms of the sequence - Colin Barker, Jul 12 2013 LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2,0,-2,2,-2,0,2,-1). FORMULA G.f.: -(x^8-9*x^6-5*x^2-1)/(1-x^2)^2/(1-x^4)/(1-x^8). G.f.: -(x^4-9*x^3-5*x-1) / ((x-1)^4*(x+1)^2*(x^2+1)). - Colin Barker, Jul 12 2013 EXAMPLE There are 7 symmetric (3,2)-hypergraphs under action of complementing group C(3,2): {{1,2},{1,2,3}}, {{1,3},{1,2,3}}, {{1,2},{1,3}}, {{2,3},{1,2,3}}, {{1,2},{2,3}}, {{1,3},{2,3}}, {{1},{2,3}}. MAPLE gf := -(x^8-9*x^6-5*x^2-1)/(1-x^2)^2/(1-x^4)/(1-x^8): s := series(gf, x, 200): for i from 0 to 200 by 2 do printf(`%d, `, coeff(s, x, i)) od: MATHEMATICA LinearRecurrence[{2, 0, -2, 2, -2, 0, 2, -1}, {1, 7, 14, 35, 57, 98, 140, 210}, 50] (* Harvey P. Dale, May 15 2020 *) CROSSREFS Sequence in context: A293359 A134384 A304143 * A161814 A333594 A067048 Adjacent sequences:  A055777 A055778 A055779 * A055781 A055782 A055783 KEYWORD nonn,easy AUTHOR Vladeta Jovovic, Jul 13 2000 EXTENSIONS More terms from James A. Sellers, Jul 13 2000 More terms from Colin Barker, Jul 12 2013 STATUS approved

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Last modified October 26 02:11 EDT 2020. Contains 338026 sequences. (Running on oeis4.)