A107962 a(n) = (n+1)(n+2)^2*(n+3)(n+4)(5n^2 + 18n + 15)/720.

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

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

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

Adjacent sequences: A107959 A107960 A107961 * A107963 A107964 A107965

Keyword

nonn,easy

Author

Emeric Deutsch, Jun 12 2005

Status

approved