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A109109
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a(n)=10a(n-1)+a(n-2), a(0)=1,a(1)=4.
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0
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1, 4, 41, 414, 4181, 42224, 426421, 4306434, 43490761, 439214044, 4435631201, 44795526054, 452390891741, 4568704443464, 46139435326381, 465963057707274, 4705770012399121, 47523663181698484, 479942401829383961
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Kekule numbers for certain benzenoids.
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REFERENCES
| S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p.284, K{Q_2(n)}).
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LINKS
| Tanya Khovanova, Recursive Sequences
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FORMULA
| a(n)=(1/2/sqrt(26))((sqrt(26)-1)(5+sqrt(26))^n+(sqrt(26)+1)(5-sqrt(26))^n) G.f.=(1-6*z)/(1-10z-z^2)
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MAPLE
| a:=n->(1/2/sqrt(26))*((sqrt(26)-1)*(5+sqrt(26))^n+(sqrt(26)+1)*(5-sqrt(26))^n): seq(expand(a(n)), n=0..20);
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CROSSREFS
| Sequence in context: A089664 A089454 A193368 * A114467 A118450 A024383
Adjacent sequences: A109106 A109107 A109108 * A109110 A109111 A109112
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KEYWORD
| nonn
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AUTHOR
| Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 19 2005
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