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 A108683 a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(7*n^2 + 20*n + 15)/360. 0
 1, 14, 83, 322, 966, 2436, 5418, 10956, 20559, 36322, 61061, 98462, 153244, 231336, 340068, 488376, 687021, 948822, 1288903, 1724954, 2277506, 2970220, 3830190, 4888260, 6179355, 7742826, 9622809, 11868598, 14535032, 17682896, 21379336 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Kekulé numbers for certain benzenoids. REFERENCES S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 233, # 8). LINKS FORMULA G.f.: (1+x)*(1+6*x)/(1-x)^7. MAPLE G:=factor(sum(a(n)*z^n, n=0..infinity)); series(G, z=0, 37); CROSSREFS Sequence in context: A176010 A250562 A166819 * A323415 A166389 A085036 Adjacent sequences:  A108680 A108681 A108682 * A108684 A108685 A108686 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Jun 18 2005 STATUS approved

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Last modified December 14 12:04 EST 2019. Contains 329979 sequences. (Running on oeis4.)