information:extraction, structural:expansion
Relation to discrete-time Fourier transform

When the series converges absolutely, G (a n; e − i ω) = ∑ n = 0 ∞ a n e − i ω n {\displaystyle G\left(a_{n};e^{-i\omega }\right)=\sum _{n=0}^{\infty }a_{n}e^{-i\omega n}} is the discrete-time Fourier transform of the sequence a, a,....