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A014717
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a(n) = (F(n+1) + L(n))^2 where F(n) are the Fibonacci numbers (A000045) and L(n) are the Lucas numbers (A000032).
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1
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9, 4, 25, 49, 144, 361, 961, 2500, 6561, 17161, 44944, 117649, 308025, 806404, 2111209, 5527201, 14470416, 37884025, 99181681, 259660996, 679801329, 1779742969, 4659427600, 12198539809, 31936191849, 83610035716, 218893915321, 573071710225, 1500321215376
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 2*a(n-1) + 2*a(n-2) - a(n-3). - Colin Barker, Apr 23 2015
G.f.: (9 - 14*x - x^2)/ ((1+x)*(1-3*x+x^2)). - Colin Barker, Apr 23 2015
a(n) = (1/5)*(22*(-1)^n + 19*Fibonacci(2*n) + 23*Fibonacci(2*n-1)). - Ehren Metcalfe, Mar 26 2016
a(n) = (2^(-1-n)*(11*(-1)^n*2^(2+n) + (23-3*sqrt(5))*(3-sqrt(5))^n + (3+sqrt(5))^n*(23+3*sqrt(5))))/5. - Colin Barker, Oct 01 2016
a(n) = 3*a(n-1) - a(n-2) + 22*(-1)^n. - Greg Dresden, May 18 2020
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MATHEMATICA
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PROG
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(PARI) lucas(n) = if(n==0, 2, fibonacci(2*n)/fibonacci(n))
a(n) = (fibonacci(n+1)+lucas(n))^2 \\ Colin Barker, Apr 24 2015
(PARI) Vec( (9-14*x-x^2)/((1+x)*(1-3*x+x^2)) + O(x^30)) \\ Colin Barker, Apr 23 2015
(PARI) a(n) = (2*fibonacci(n+1)+fibonacci(n-1))^2
(Magma) [(Fibonacci(n+1) + Lucas(n))^2: n in [0..30]]; // Vincenzo Librandi, Apr 25 2015
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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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