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

Author

Emeric Deutsch, Jun 12 2005

Keywords

• nonn
• easy

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).

Programs

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);

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