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A110698
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Kekulé numbers for certain benzenoids of trigonal symmetry.
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1
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9, 104, 3724, 152978, 6772428, 318919354, 15762420826, 808272767014, 42631956711628, 2298618088718378, 126131492134695474, 7020934326396461014, 395480502329858803674, 22501172037539767125398
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OFFSET
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0,1
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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 (see p. 313).
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 0..550
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FORMULA
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a(n) = 20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2.
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MAPLE
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a:=n->20*binomial(2*n, n)^3-18*binomial(2*n, n)^2+9*binomial(2*n, n)-2; seq(a(n), n=0..16);
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MATHEMATICA
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Table[20*Binomial[2*n, n]^3 - 18*Binomial[2*n, n]^2 + 9*Binomial[2*n, n] - 2, {n, 0, 50}] (* G. C. Greubel, Sep 06 2017 *)
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PROG
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(PARI) for(n=0, 25, print1(20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2, ", ")) \\ G. C. Greubel, Sep 06 2017
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CROSSREFS
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Sequence in context: A356244 A081461 A231646 * A012485 A052503 A261428
Adjacent sequences: A110695 A110696 A110697 * A110699 A110700 A110701
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch, Aug 03 2005
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STATUS
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approved
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