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A200408
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a(n) = -4 + 5*Fibonacci(n+1)^2.
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0
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1, 1, 16, 41, 121, 316, 841, 2201, 5776, 15121, 39601, 103676, 271441, 710641, 1860496, 4870841, 12752041, 33385276, 87403801, 228826121, 599074576, 1568397601, 4106118241, 10749957116, 28143753121, 73681302241, 192900153616, 505019158601, 1322157322201
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OFFSET
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0,3
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COMMENTS
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a(1) and a(2n) are perfect squares.
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LINKS
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FORMULA
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a(n) = 3*a(n-1)-3*a(n-3)+a(n-4). G.f.: 1-x*(x^3-7*x^2+13*x+1) / ((x-1)*(x+1)*(x^2-3*x+1)). - Colin Barker, Sep 01 2013
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MATHEMATICA
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Table[-4 + 5*Fibonacci[n]^2, {n, 2, 31}] (* Alonso del Arte, Nov 17 2011 *)
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PROG
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(PARI) Vec(-x*(x^3-7*x^2+13*x+1)/((x-1)*(x+1)*(x^2-3*x+1)) + O(x^100)) \\ Colin Barker, Sep 01 2013
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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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