A107965 a(n) = (n+1)(n+2)^2*(n+3)^2*(n+4)(11n^4 + 110n^3 + 439n^2 + 820n + 600)/86400.

1, 33, 421, 3171, 16954, 71148, 249228, 758934, 2066559, 5135845, 11828817, 25546885, 52216164, 101751664, 190171248, 342572508, 597234429, 1011161361, 1667449861, 2684929863, 4230610846, 6535551660, 9914869900, 14792713650, 21733135515, 31477936581

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

T. D. Noe, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).

Formula

G.f.: -(x^6+22*x^5+113*x^4+190*x^3+113*x^2+22*x+1) / (x-1)^11. - Colin Barker, Aug 13 2013

Maple

a:=n->(1/86400)*(n+1)*(n+2)^2*(n+3)^2*(n+4)*(11*n^4+110*n^3+439*n^2+820*n+600): seq(a(n), n=0..26);

Crossrefs

Sequence in context: A202256 A324950 A252925 * A220591 A296839 A296988

Adjacent sequences: A107962 A107963 A107964 * A107966 A107967 A107968

Keyword

nonn,easy

Author

Emeric Deutsch, Jun 12 2005

Status

approved