ȿθΨŪõˡ.

ѴˡѤաꥨڥȥˡǤȿ N ȥǥʻ L, Ѵˡɬפʳʻ J δ֤˰ʲδط.

L = 2 * N + 1
J = 3 * N + 1

⤷, ǥγʻ (⤷ϥǥη׻ΰȶֲ) ͿƤʤ, L ΤǤ. 
ѴˡѤʬǤ FFT ٤⤤Τ, FFT ΨŪѤ뤿ˤ, J  2, 3, 5, 7 Τ٤ǹƤ뤳Ȥ˾ޤ.
Ĥޤ, Ϳ׻ΰζֳʻ L ˺ǤᤤŬ N 

J = 2^a * 3^b * 5^c * 7^d

,

N = ( J - 1 ) / 3

ǤФ褤. 
ϤĤޤ, Ǥդǰʬ򤷤, 

(1)  A  2^a * 3^b * 5^c * 7^d 
(2) A - 1 ǰ 3  1 ĤǤޤޤƤ

 A  J θȤƺŬȤȤˤʤ.

ºݤ϶ֲ٤̩˵ꤵƤ餺, FFT ǻθΨͥ褵ʤ, ֲ٤ȷ׻ΰ褫Ϳֳʻ L' ȿ N' ,  J' .
 J' μդˤĤǰʬԤ,  (1), (2) ξ A Ŭ J ȤѤ.
J  N, L ⼫ȵޤ.

㤨, ֳʻ L Ȥ 683 ͿƤ, N  341 ʤΤ, J  1024 Ȥʤ.
ξ, J = 2^10 ȤʤäƤΤ, Τޤ޺Ŭ J ȤŬѤǤ.
ʤߤ, ξǤ J - 1 = 1023 ʤΤ, 3 ܿǤ.
ȤȤ (1), (2) Ƥ. 
