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A107962
a(n) = (n+1)(n+2)^2*(n+3)(n+4)(5n^2 + 18n + 15)/720.
2
1, 19, 142, 665, 2338, 6762, 16968, 38214, 79035, 152581, 278278, 483847, 807716, 1301860, 2035104, 3096924, 4601781, 6694023, 9553390, 13401157, 18506950, 25196270, 33858760, 44957250, 59037615, 76739481, 98807814, 126105427
OFFSET
0,2
COMMENTS
Kekulé numbers for certain benzenoids.
REFERENCES
S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 229).
LINKS
FORMULA
O.g.f.: (1+11*x+18*x^2+5*x^3)/(-1+x)^8. - R. J. Mathar, Apr 07 2008
MAPLE
a:=n->(1/720)*(n+1)*(n+2)^2*(n+3)*(n+4)*(5*n^2+18*n+15): seq(a(n), n=0..30);
PROG
(Magma) [Floor((1/720)*(n+1)*(n+2)^2*(n+3)*(n+4)*(5*n^2+18*n+15)): n in [0..30]]; // Vincenzo Librandi, Mar 28 2012
CROSSREFS
Sequence in context: A201151 A221600 A110694 * A002615 A081590 A093646
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 12 2005
STATUS
approved