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A114240
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a(n) = (n+1)(n+2)^2*(n+3)(7n^2 + 23n + 20)/240.
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0
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1, 15, 94, 380, 1176, 3038, 6888, 14148, 26895, 48037, 81510, 132496, 207662, 315420, 466208, 672792, 950589, 1318011, 1796830, 2412564, 3194884, 4178042, 5401320, 6909500, 8753355, 10990161, 13684230, 16907464, 20739930, 25270456
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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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REFERENCES
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S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 168).
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LINKS
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Table of n, a(n) for n=0..29.
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
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FORMULA
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G.f.: -(2*x^3+10*x^2+8*x+1)/(x-1)^7. - Alois P. Heinz, Feb 27 2015
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MAPLE
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a:=n->(n+1)*(n+2)^2*(n+3)*(7*n^2+23*n+20)/240: seq(a(n), n=0..33);
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CROSSREFS
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Sequence in context: A125325 A126483 A226766 * A189657 A190274 A052459
Adjacent sequences: A114237 A114238 A114239 * A114241 A114242 A114243
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KEYWORD
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nonn,easy
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AUTHOR
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Emeric Deutsch, Nov 18 2005
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STATUS
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approved
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