A114239 a(n) = (n+1)(n+2)^3*(n+3)(n^2 + 4n + 5)/120.

1, 18, 136, 650, 2331, 6860, 17472, 39852, 83325, 162382, 298584, 522886, 878423, 1423800, 2236928, 3419448, 5101785, 7448874, 10666600, 15008994, 20786227, 28373444, 38220480, 50862500, 66931605, 87169446, 112440888, 143748766

Offset

0,2

Comments

Kekulé numbers for certain benzenoids.

First differences of A107891. Partial sums of A083200. - Peter Bala, Sep 21 2007

References

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 167, Table 10.5/I/6).

Links

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Formula

a(n-2) = (n^7-n^3)/(2^7-2^3). - David Radcliffe, Dec 27 2008

G.f.: (1+10*x+20*x^2+10*x^3+x^4)/(1-x)^8. - Colin Barker, Feb 09 2012

Maple

a:=n->(n+1)*(n+2)^3*(n+3)*(n^2+4*n+5)/120: seq(a(n), n=0..33);

Prog

(PARI) a(n)=n-=2; (n^7-n^3)/120 \\ Charles R Greathouse IV, Feb 09 2012

Crossrefs

Cf. A047819, A083200, A107891.

Sequence in context: A056003 A337002 A239208 * A087115 A163707 A212154

Adjacent sequences: A114236 A114237 A114238 * A114240 A114241 A114242

Keyword

nonn,easy

Author

Emeric Deutsch, Nov 18 2005

Status

approved