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A055849
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a(n)=3a(n-1)-a(n-2); a(0)=1, a(1)=9.
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3
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1, 9, 26, 69, 181, 474, 1241, 3249, 8506, 22269, 58301, 152634, 399601, 1046169, 2738906, 7170549, 18772741, 49147674, 128670281, 336863169, 881919226, 2308894509, 6044764301, 15825398394, 41431430881, 108468894249
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OFFSET
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0,2
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pps. 194-196.
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LINKS
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Table of n, a(n) for n=0..25.
Index entries for sequences related to linear recurrences with constant coefficients
Tanya Khovanova, Recursive Sequences
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FORMULA
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a(n)={9*[((3+sqrt(5))/2)^n-((3-sqrt(5))/2)^n]-[((3+sqrt(5))/2)^(n-1)-((3-sqrt(5))/2)^(n-1)]}/sqrt(5).
G.f.(x)=(1+6x)/(1-3x+x^2).
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MATHEMATICA
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LinearRecurrence[{3, -1}, {1, 9}, 40] (* Harvey P. Dale, Jan 20 2013 *)
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CROSSREFS
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Sequence in context: A154560 A048468 A048771 * A084813 A056409 A056399
Adjacent sequences: A055846 A055847 A055848 * A055850 A055851 A055852
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams, Jun 03 2000
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STATUS
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approved
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