OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
R. S. Melham, Closed Forms for Finite Sums of Weighted Products of Generalized Fibonacci Numbers, The Fibonacci Quarterly 55 (May 2017), Number 2, pages 99-104.
Index entries for linear recurrences with constant coefficients, signature (4,8,-8).
FORMULA
G.f.: 2*x/((1 + 2*x)*(1 - 6*x + 4*x^2)).
a(n) = 4*a(n-1) + 8*a(n-2) - 8*a(n-3).
a(n) = ((1+sqrt(5))^(2*n+1) + (1-sqrt(5))^(2*n+1))/(10*2^n) - (-2)^n/5, therefore 5*a(n) + (-2)^n = A082762(n). - Bruno Berselli, Sep 13 2017
MATHEMATICA
Table[2^n Fibonacci[n] Fibonacci[n+1], {n, 0, 40}]
Table[((1 + Sqrt[5])^(2 n + 1) + (1 - Sqrt[5])^(2 n + 1))/(10 2^n) - (-2)^n/5, {n, 0, 30}] (* Bruno Berselli, Sep 13 2017 *)
PROG
(Magma) [2^n*Fibonacci(n)*Fibonacci(n+1): n in [0..30]];
(PARI) a(n) = 2^n*fibonacci(n)*fibonacci(n+1); \\ Altug Alkan, Sep 13 2017
(Sage) [2^n*fibonacci(n)*fibonacci(n+1) for n in range(30)] # Bruno Berselli, Sep 13 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Sep 13 2017
STATUS
approved