A181358 Number of twiddle factors in the first stage of a Pease Radix 4 Fast Fourier Transform.

8, 44, 188, 764, 3068, 12284, 49148, 196604, 786428, 3145724, 12582908, 50331644, 201326588, 805306364, 3221225468, 12884901884, 51539607548, 206158430204, 824633720828, 3298534883324, 13194139533308, 52776558133244, 211106232532988, 844424930131964

Offset

0,1

Comments

Number of twiddle factors in the first stage of a Pease Radix 4 Fast Fourier Transform.

Links

Colin Barker, Table of n, a(n) for n = 0..1000

Wikipedia, Twiddle factor

Index entries for linear recurrences with constant coefficients, signature (5,-4).

Formula

a(n) = 4*(3*4^n - 1).

From Colin Barker, Nov 26 2016: (Start)

a(n) = 4*A198693(n).

a(n) = 5*a(n-1) - 4*a(n-2) for n>1.

G.f.: 4*(2+x) / ((1-x) * (1-4*x)).

(End)

Prog

(PARI) Vec(4*(2+x) / ((1-x) * (1-4*x)) + O(x^30)) \\ Colin Barker, Nov 26 2016

Crossrefs

Sequence in context: A059596 A327386 A341386 * A005798 A092877 A160521

Adjacent sequences: A181355 A181356 A181357 * A181359 A181360 A181361

Keyword

nonn,easy

Author

Robert Koutsoyannis (bob.koutsoyannis(AT)gmail.com), Oct 14 2010

Status

approved