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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
OFFSET
0,2
COMMENTS
Kekulé numbers for certain benzenoids.
LINKS
S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 230).
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 A372996 A248490
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 12 2005
STATUS
approved