$\zeta(s)L(s,\chi_1)L(s,\chi_2)L(s,\chi_1\chi_2)$ is a Dirichlet series with nonnegative coefficients and $a_1 = 1$ (Davenport §21)

Initializing...

$\zeta(s)L(s,\chi_1)L(s,\chi_2)L(s,\chi_1\chi_2)$ is a Dirichlet series with nonnegative coefficients and $a_1 = 1$ (Davenport §21) · Prove2Me