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Let (A), (B) and (C) be sequences of the Fibonacci type, x = {1, 2, ...}, y = {0, 1, ...}. Form the three sequences with the initial values A(0) = x, A(1) = y, B(0) = 7*x - y, B(1) = 11*x, C(0) = A(n), C(1) = B(n). Then a(n) = C(n)/x always applies. - Klaus Purath, Oct 28 2019
From Klaus Purath, Oct 28 2019: (Start)
a(n) = (a(n-2) - a(n-1) - a(n+1) + a(n+2))/4.
(a(n-3) - a(n-2) - a(n-1) + a(n))/6 = Fibonacci(2*n-2).
(a(n-5) + a(n))/30 = Fibonacci(2*n-4).
(a(n) - a(n-4))/18 = Fibonacci(2*n-3). (End)
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LinearRecurrence[{2, 2, -1}, {1, 5, 13}, 30] (* Harvey P. Dale, Jul 12 2019 *)
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a:= n-> (<<0|1|0>, <0|0|1>, <-1|2|2>>^n. <<1, 5, 13>>)[1, 1]:
seq(a(n), n=0..30); # Alois P. Heinz, Sep 28 2016
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(PARI) for(n=0, 30, print1(6*fibonacci(n)*fibonacci(n+1)+(-1)^n", "));
(PARI) for(n=0, 30, print1(6*fibonacci(n)*fibonacci(n+1)+(-1)^n", "));
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