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A109111 a(n) = (1/sqrt(595))((sqrt(595) + 26)(125 + 5sqrt(595))^n + (sqrt(595) - 26)(125 - 5sqrt(595))^n). 0
2, 510, 126000, 31117500, 7684875000, 1897880625000, 468706500000000, 115753214531250000, 28586773757812500000, 7059878528554687500000, 1743529551820312500000000, 430587479058662109375000000 (list; graph; refs; listen; history; text; internal format)
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).

LINKS

Table of n, a(n) for n=0..11.

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: A172232 A253706 A109032 * A004886 A234606 A139302

Adjacent sequences:  A109108 A109109 A109110 * A109112 A109113 A109114

KEYWORD

nonn

AUTHOR

Emeric Deutsch, Jun 19 2005

STATUS

approved

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Last modified May 29 04:13 EDT 2020. Contains 334696 sequences. (Running on oeis4.)