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A107969 a(n) = (n+1)(n+2)^2*(n+3)(2n+3)(5n^2 + 19n + 20)/720. 1
1, 22, 182, 915, 3388, 10192, 26376, 60894, 128535, 252406, 467038, 822185, 1387386, 2257360, 3558304, 5455164, 8159949, 11941158, 17134390, 24154207, 33507320, 45807168, 61789960, 82332250, 108470115, 141420006, 182601342 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Kekulé numbers for certain benzenoids.

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 230).

Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

FORMULA

From Colin Barker, Apr 22 2020: (Start)

G.f.: (1 + 14*x + 34*x^2 + 19*x^3 + 2*x^4) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>7.

(End)

MAPLE

a:=n->(1/720)*(n+1)*(n+2)^2*(n+3)*(2*n+3)*(5*n^2+19*n+20): seq(a(n), n=0..30);

PROG

(PARI) Vec((1 + 14*x + 34*x^2 + 19*x^3 + 2*x^4) / (1 - x)^8 + O(x^30)) \\ Colin Barker, Apr 22 2020

CROSSREFS

Sequence in context: A125359 A126517 A197496 * A248489 A248490 A191012

Adjacent sequences:  A107966 A107967 A107968 * A107970 A107971 A107972

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, Jun 12 2005

STATUS

approved

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Last modified October 23 08:40 EDT 2021. Contains 348211 sequences. (Running on oeis4.)