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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

%I

%S 1,21,157,707,2353,6405,15106,31998,62349,113641,196119,323401,513149,

%T 787801,1175364,1710268,2434281,3397485,4659313,6289647,8369977,

%U 10994621,14272006,18326010,23297365,29345121,36648171,45406837

%N a(n) = (n+1)*(n+2)*(61*n^4 + 366*n^3 + 845*n^2 + 888*n + 360)/720.

%C Kekulé numbers for certain benzenoids.

%D S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 231, # 35).

%H R. P. Stanley, <a href="/A002721/a002721.pdf">Examples of Magic Labelings</a>, Unpublished Notes, 1973 [Cached copy, with permission] See p. 31.

%F G.f.: (1 + 14*x + 31*x^2 + 14*x^3 + x^4)/(1-x)^7.

%p 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);

%K nonn,easy

%O 0,2

%A _Emeric Deutsch_, Jun 17 2005

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Last modified January 26 01:48 EST 2020. Contains 331270 sequences. (Running on oeis4.)