

A114239


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


2



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
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OFFSET

0,2


COMMENTS

KekulĂ© numbers for certain benzenoids.
First differences of A107891. Partial sums of A083200.  Peter Bala, Sep 21 2007


REFERENCES

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


LINKS

Table of n, a(n) for n=0..27.


FORMULA

a(n2) = (n^7n^3)/(2^72^3).  David Radcliffe, Dec 27 2008
G.f.: (1+10*x+20*x^2+10*x^3+x^4)/(1x)^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^7n^3)/120 \\ Charles R Greathouse IV, Feb 09 2012


CROSSREFS

Cf. 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



