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A055780 Number of symmetric types of (3,2n)-hypergraphs under action of complementing group C(3,2). 0
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

Table of n, a(n) for n=0..43.

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:

CROSSREFS

Sequence in context: A293359 A134384 A304143 * A161814 A067048 A189046

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 September 20 22:20 EDT 2019. Contains 327252 sequences. (Running on oeis4.)