In the field of mathematical analysis, a general Dirichlet series is an infinite series that takes the form of ∑ n = 1 ∞ a n e − λ n s, {\displaystyle \sum _{n=1}^{\infty }a_{n}e^{-\lambda _{n}s},} where a n {\displaystyle a_{n}}, s {\displaystyle s} are complex numbers and { λ n } {\displaystyle \{\lambda _{n}\}} is a strictly increasing sequence of nonnegative real numbers that tends to infinity. Wikipedia