A109117 a(n) = (n+1)^3*(2n+1)(5n+1).

1, 144, 1485, 7168, 23625, 61776, 138229, 276480, 508113, 874000, 1425501, 2225664, 3350425, 4889808, 6949125, 9650176, 13132449, 17554320, 23094253, 29952000, 38349801, 48533584, 60774165, 75368448, 92640625, 112943376

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. 310).

Links

Table of n, a(n) for n=0..25.

Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

Formula

G.f.: (1 + 138z + 636z^2 + 398z^3 + 27z^4)/(1-z)^6.

Maple

a:=n->(n+1)^3*(2*n+1)*(5*n+1): seq(a(n), n=0..30);

Mathematica

Table[(2n + 1)(5n + 1)(n + 1)^3, {n, 0, 30}] (* Wesley Ivan Hurt, Jan 24 2014 *)

Crossrefs

Sequence in context: A223435 A169859 A137416 * A209205 A223594 A223445

Adjacent sequences: A109114 A109115 A109116 * A109118 A109119 A109120

Keyword

nonn,easy

Author

Emeric Deutsch, Jun 19 2005

Status

approved