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A107916 a(n) = binomial(n+3,2)*binomial(n+4,3)*binomial(n+5,5)/12. 1
1, 30, 350, 2450, 12348, 49392, 166320, 490050, 1297725, 3149146, 7105098, 15071420, 30321200, 58262400, 107535744, 191548044, 330569505, 554550150, 906840550, 1449035742, 2267198780, 3479762000, 5247450000, 7785618750, 11379460365, 16402583106, 23339541330 (list; graph; refs; listen; history; text; internal format)
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. 229).

LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).

FORMULA

a(n) = (1/17280)(n+1)(n+2)^3*(n+3)^3*(n+4)^2*(n+5).

G.f.: -(2*x^5+28*x^4+85*x^3+75*x^2+19*x+1)/(x-1)^11. - Colin Barker, Sep 20 2012

MAPLE

a:=n->(1/12)*binomial(n+3, 2)*binomial(n+4, 3)*binomial(n+5, 5): seq(a(n), n=0..30);

CROSSREFS

Sequence in context: A115500 A214085 A125418 * A091775 A222086 A008656

Adjacent sequences:  A107913 A107914 A107915 * A107917 A107918 A107919

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, Jun 12 2005

STATUS

approved

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Last modified September 19 15:43 EDT 2020. Contains 337178 sequences. (Running on oeis4.)