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A114240
a(n) = (n+1)(n+2)^2*(n+3)(7n^2 + 23n + 20)/240.
0
1, 15, 94, 380, 1176, 3038, 6888, 14148, 26895, 48037, 81510, 132496, 207662, 315420, 466208, 672792, 950589, 1318011, 1796830, 2412564, 3194884, 4178042, 5401320, 6909500, 8753355, 10990161, 13684230, 16907464, 20739930, 25270456
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. 168).
FORMULA
G.f.: -(2*x^3+10*x^2+8*x+1)/(x-1)^7. - Alois P. Heinz, Feb 27 2015
MAPLE
a:=n->(n+1)*(n+2)^2*(n+3)*(7*n^2+23*n+20)/240: seq(a(n), n=0..33);
CROSSREFS
Sequence in context: A125325 A126483 A226766 * A189657 A190274 A374808
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Nov 18 2005
STATUS
approved