Gauss sum of a Dirichlet character
= Gauss sum of a Dirichlet character
{title2=$g(\chi)=\sum_{a\bmod N}\chi(a)e^{2\pi ia/N}$}
Extend a <Dirichlet character> by zero on nonunits. Its Gauss sum is $g(\chi)=\sum_{a\bmod N}\chi(a)e^{2\pi ia/N}$, and its finite Fourier transform at $r$ is $S_\chi(r)=\sum_{a\bmod N}\chi(a)e^{2\pi ira/N}$.