OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..58
FORMULA
a(n) = 4^(n-1)*a(n-1) + a(n-2).
EXAMPLE
G.f. = x + 5*x^2 + 81*x^3 + 5189*x^4 + 1328465*x^5 + 1360353349*x^6 + ...
a(3) = 81, the numerator of 1 + 1/(4 + 1/16) = 81/65.
MATHEMATICA
f[n_] := Numerator[ FromContinuedFraction[ Reverse[4^Range[0, n -1]] ]]; Array[f, 12] (* Robert G. Wilson v, Dec 29 2016 *)
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Seiichi Manyama, Dec 29 2016
STATUS
approved