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Search: id:A109113
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| A109113 |
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a(n)=6a(n-1)+3a(n-2), a(0)=2, a(1)=14. |
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+0
1
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| 2, 14, 90, 582, 3762, 24318, 157194, 1016118, 6568290, 42458094, 274453434, 1774094886, 11467929618, 74129862366, 479182963050, 3097487365398, 20022473081538, 129427300585422, 836631222757146, 5408069238299142
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OFFSET
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0,1
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COMMENT
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Kekule numbers for certain benzenoids.
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REFERENCES
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S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (pp. 302, P_{15}).
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FORMULA
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a(n)=[(3+2sqrt(3))^(n+1)+(3-2sqrt(3))^(n+1)]/3. G=2(1+z)/(1-6z-3z^2).
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MAPLE
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a[0]:=2: a[1]:=14: for n from 2 to 25 do a[n]:=6*a[n-1]+3*a[n-2] od: seq(a[n], n=0..22);
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CROSSREFS
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Sequence in context: A162478 A065892 A139183 this_sequence A081959 A002464 A020063
Adjacent sequences: A109110 A109111 A109112 this_sequence A109114 A109115 A109116
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 19 2005
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