login
A109111
a(n) = (1/sqrt(595))*((sqrt(595) + 26)*(125 + 5*sqrt(595))^n + (sqrt(595) - 26)*(125 - 5*sqrt(595))^n).
0
2, 510, 126000, 31117500, 7684875000, 1897880625000, 468706500000000, 115753214531250000, 28586773757812500000, 7059878528554687500000, 1743529551820312500000000, 430587479058662109375000000
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. 292).
FORMULA
G.f.: 2(1+5z)/(1 - 250z + 750z^2).
MAPLE
a:=n->(1/sqrt(595))*((sqrt(595)+26)*(125+5*sqrt(595))^n+(sqrt(595)-26)*(125-5*sqrt(595))^n): seq(expand(a(n)), n=0..13);
CROSSREFS
Sequence in context: A253706 A109032 A362539 * A004886 A234606 A139302
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 19 2005
STATUS
approved