

A109107


a(n) = (1/sqrt(26))((5+sqrt(26))^(n+1)(5sqrt(26))^(n+1)).


0



2, 20, 202, 2040, 20602, 208060, 2101202, 21220080, 214302002, 2164240100, 21856703002, 220731270120, 2229169404202, 22512425312140, 227353422525602, 2296046650568160, 23187819928207202, 234174245932640180
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OFFSET

0,1


COMMENTS

a(n) = 2*A041041(n). KekulĂ© numbers for certain benzenoids.


REFERENCES

S. J. Cyvin and I. Gutman, KekulĂ© structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 284, K{Q(n)}).


LINKS

Table of n, a(n) for n=0..17.
Tanya Khovanova, Recursive Sequences
Index entries for linear recurrences with constant coefficients, signature (10, 1).


FORMULA

G.f.: 2/(110zz^2).


MAPLE

a:=n>(1/sqrt(26))*((5+sqrt(26))^(n+1)(5sqrt(26))^(n+1)): seq(expand(a(n)), n=0..20);


CROSSREFS

Cf. A041041.
Sequence in context: A093136 A037519 A037722 * A037729 A037624 A077327
Adjacent sequences: A109104 A109105 A109106 * A109108 A109109 A109110


KEYWORD

nonn


AUTHOR

Emeric Deutsch, Jun 19 2005


STATUS

approved



