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A107969
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a(n) = (n+1)(n+2)^2*(n+3)(2n+3)(5n^2 + 19n + 20)/720.
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1
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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
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OFFSET
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0,2
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COMMENTS
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Kekulé numbers for certain benzenoids.
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LINKS
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FORMULA
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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)
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MAPLE
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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);
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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