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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

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. 231, # 35).

LINKS

Table of n, a(n) for n=0..27.

R. P. Stanley, Examples of Magic Labelings, Unpublished Notes, 1973 [Cached copy, with permission] See p. 31.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.)