%I #14 Nov 26 2016 11:35:04
%S 8,44,188,764,3068,12284,49148,196604,786428,3145724,12582908,
%T 50331644,201326588,805306364,3221225468,12884901884,51539607548,
%U 206158430204,824633720828,3298534883324,13194139533308,52776558133244,211106232532988,844424930131964
%N Number of twiddle factors in the first stage of a Pease Radix 4 Fast Fourier Transform.
%C Number of twiddle factors in the first stage of a Pease Radix 4 Fast Fourier Transform.
%H Colin Barker, <a href="/A181358/b181358.txt">Table of n, a(n) for n = 0..1000</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Twiddle_factor">Twiddle factor</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-4).
%F a(n) = 4*(3*4^n - 1).
%F From _Colin Barker_, Nov 26 2016: (Start)
%F a(n) = 4*A198693(n).
%F a(n) = 5*a(n-1) - 4*a(n-2) for n>1.
%F G.f.: 4*(2+x) / ((1-x) * (1-4*x)).
%F (End)
%o (PARI) Vec(4*(2+x) / ((1-x) * (1-4*x)) + O(x^30)) \\ _Colin Barker_, Nov 26 2016
%K nonn,easy
%O 0,1
%A Robert Koutsoyannis (bob.koutsoyannis(AT)gmail.com), Oct 14 2010