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A109122
a(n) = 4*(n+1)^2*(3*n+1)^2*(12*n^2+20*n+5).
0
20, 9472, 164052, 1107200, 4681300, 14929920, 39411092, 90821632, 188932500, 362835200, 653499220, 1116640512, 1825901012, 2876339200, 4388231700, 6511185920, 9428563732, 13362216192, 18577529300, 25388780800, 34164808020
OFFSET
0,1
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. 311).
FORMULA
G.f.: 4*(5 + 2333*z + 24542*z^2 + 39262*z^3 + 11293*z^4 + 325*z^5)/(1-z)^7.
MAPLE
a:=n->4*(n+1)^2*(3*n+1)^2*(12*n^2+20*n+5): seq(a(n), n=0..24);
MATHEMATICA
Table[4(n+1)^2(3n+1)^2(12n^2+20n+5), {n, 0, 30}] (* Harvey P. Dale, Jun 14 2019 *)
CROSSREFS
Sequence in context: A293286 A250021 A203308 * A135420 A045811 A086687
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 19 2005
STATUS
approved