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

Author

N. J. A. Sloane, Oct 10 2006

Keywords

• nonn
• easy

Links

• 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).

Programs

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

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