The n×n square matrix F_n with entries given by F_(j k) = e^(2π i j k/n) congruent ω^(j k) for j, k = 0, 1, 2, ..., n - 1, where i is the imaginary number i = sqrt(-1), and normalized by 1/sqrt(n) to make it a unitary.

fast Fourier transform | Fourier transform