A123351 Kekulé numbers for certain benzenoids (see the Cyvin-Gutman book for details).

1, 4, 30, 146, 517, 1476, 3614, 7890, 15761, 29332, 51526, 86274, 138725, 215476, 324822, 477026, 684609, 962660, 1329166, 1805362, 2416101, 3190244, 4161070, 5366706, 6850577, 8661876, 10856054, 13495330, 16649221, 20395092, 24818726

Offset

0,2

Links

Table of n, a(n) for n=0..30.

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 120 and K{Ch(m,3)} page 119).

Formula

G.f.: -x*(2*x^6-8*x^5+20*x^4-15*x^3+23*x^2-3*x+1) / (x-1)^7. - Colin Barker, Aug 29 2013

Maple

A123351 := proc(n)
    (n^6+6*n^5+22*n^4+30*n^3+49*n^2+36)/36 ;
end proc:
seq( A123351(n), n=0..30) ; # R. J. Mathar, Jul 26 2019

Crossrefs

Sequence in context: A375260 A305764 A317113 * A305525 A316999 A217213

Adjacent sequences: A123348 A123349 A123350 * A123352 A123353 A123354

Keyword

nonn,easy

Author

N. J. A. Sloane, Oct 10 2006

Status

approved