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A081006
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a(n) = Fibonacci(4n) - 1, or Fibonacci(2n+1)*Lucas(2n-1).
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2
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2, 20, 143, 986, 6764, 46367, 317810, 2178308, 14930351, 102334154, 701408732, 4807526975, 32951280098, 225851433716, 1548008755919, 10610209857722, 72723460248140, 498454011879263, 3416454622906706, 23416728348467684, 160500643816367087
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OFFSET
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1,1
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COMMENTS
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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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FORMULA
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a(n) = 8*a(n-1) - 8*a(n-2) + a(n-3).
G.f.: x*(2+4*x-x^2)/((1-x)*(1-7*x+x^2)). - Colin Barker, Jun 24 2012
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MAPLE
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with(combinat) for n from 0 to 30 do printf(`%d, `, fibonacci(4*n)-1) od # James A. Sellers, Mar 03 2003
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MATHEMATICA
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Fibonacci[4*Range[30]]-1 (* or *) LinearRecurrence[{8, -8, 1}, {2, 20, 143}, 30] (* Harvey P. Dale, Mar 19 2018 *)
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PROG
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(PARI) vector(30, n, fibonacci(4*n)-1) \\ G. C. Greubel, Jul 15 2019
(Sage) [fibonacci(4*n)-1 for n in (1..30)] # G. C. Greubel, Jul 15 2019
(GAP) List([1..30], n-> Fibonacci(4*n)-1); # G. C. Greubel, Jul 15 2019
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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