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A081079
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Lucas(4n+2)-3, or 5*Fibonacci(2n)*Fibonacci(2n+2).
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0
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0, 15, 120, 840, 5775, 39600, 271440, 1860495, 12752040, 87403800, 599074575, 4106118240, 28143753120, 192900153615, 1322157322200, 9062201101800, 62113250390415, 425730551631120, 2918000611027440, 20000273725560975
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OFFSET
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0,2
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REFERENCES
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Hugh C. Williams, Edouard Lucas and Primality Testing, John Wiley and Sons, 1998, p. 75
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LINKS
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Table of n, a(n) for n=0..19.
Index to sequences with linear recurrences with constant coefficients, signature (8,-8,1). [From R. J. Mathar, Sep 03 2010]
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FORMULA
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a(n) = 8a(n-1)-8a(n-2)+a(n-3)
a(n)=-3+(3/2)*{[(7/2)-(3/2)*sqrt(5)]^n+[(7/2)+(3/2)*sqrt(5)]^n}+(1/2)*sqrt(5)*{[(7/2)+(3/2)*sqrt(5)]^n -[(7/2)-(3/2)*sqrt(5)]^n}, with n>=0 [From Paolo P. Lava, Dec 01 2008]
G.f.: -15*x/(x-1)/(x^2-7*x+1). a(n) = 15*A092521(n) = 5*A058038(n). [From R. J. Mathar, Sep 03 2010]
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MAPLE
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luc := proc(n) option remember: if n=0 then RETURN(2) fi: if n=1 then RETURN(1) fi: luc(n-1)+luc(n-2): end: for n from 0 to 40 do printf(`%d, `, luc(4*n+2)-3) od:
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CROSSREFS
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Cf. A000032 (Lucas numbers), A000045 (Fibonacci numbers).
Sequence in context: A162635 A010967 A022580 * A138424 A120794 A038743
Adjacent sequences: A081076 A081077 A081078 * A081080 A081081 A081082
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KEYWORD
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nonn,easy
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AUTHOR
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R. K. Guy, Mar 04, 2003
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EXTENSIONS
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More terms and Maple code from James A. Sellers, Mar 05, 2003
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STATUS
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approved
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