A108677 a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(19*n^2 + 47*n + 30)/720.

1, 16, 100, 399, 1218, 3108, 6972, 14190, 26763, 47476, 80080, 129493, 202020, 305592, 450024, 647292, 911829, 1260840, 1714636, 2296987, 3035494, 3961980, 5112900, 6529770, 8259615, 10355436, 12876696, 15889825, 19468744, 23695408

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. 231, # 41).

Links

Table of n, a(n) for n=0..29.

Formula

G.f.: (1 + 9*x + 9*x^2)/(1-x)^7.

Maple

a:=n->(n+1)*(n+2)*(n+3)*(n+4)*(19*n^2+47*n+30)/720: seq(a(n), n=0..33);

Mathematica

Table[(n+1)(n+2)(n+3)(n+4)(19n^2+47n+30)/720, {n, 0, 40}]  (* Harvey P. Dale, Mar 04 2011 *)

Crossrefs

Sequence in context: A045784 A354877 A016958 * A001249 A014796 A052206

Adjacent sequences: A108674 A108675 A108676 * A108678 A108679 A108680

Keyword

nonn,easy

Author

Emeric Deutsch, Jun 17 2005

Status

approved