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 A108675 a(n) = (n+1)*(n+2)*(61*n^4 + 366*n^3 + 845*n^2 + 888*n + 360)/720. 0
 1, 21, 157, 707, 2353, 6405, 15106, 31998, 62349, 113641, 196119, 323401, 513149, 787801, 1175364, 1710268, 2434281, 3397485, 4659313, 6289647, 8369977, 10994621, 14272006, 18326010, 23297365, 29345121, 36648171, 45406837 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS KekulĂ© numbers for certain benzenoids. REFERENCES S. J. Cyvin and I. Gutman, KekulĂ© structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 231, # 35). LINKS R. P. Stanley, Examples of Magic Labelings, Unpublished Notes, 1973 [Cached copy, with permission] See p. 31. FORMULA G.f.: (1 + 14*x + 31*x^2 + 14*x^3 + x^4)/(1-x)^7. MAPLE a:=n->(n+1)*(n+2)*(61*n^4+366*n^3+845*n^2+888*n+360)/720: seq(a(n), n=0..32); CROSSREFS Sequence in context: A301883 A302080 A180374 * A296832 A267473 A179097 Adjacent sequences:  A108672 A108673 A108674 * A108676 A108677 A108678 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Jun 17 2005 STATUS approved

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Last modified December 14 19:27 EST 2019. Contains 329987 sequences. (Running on oeis4.)