Dirichlet eta function

English

Etymology

Named after Johann Peter Gustav Lejeune Dirichlet (1805–1859), German mathematician.

Proper noun

Dirichlet eta function

1. (mathematics, mathematical analysis) The alternating sum of the Dirichlet series expansion of the Riemann zeta function: $\eta (s)=\sum _{n=1}^{\infty }{(-1)^{n-1} \over n^{s}}={\frac {1}{1^{s}}}-{\frac {1}{2^{s}}}+{\frac {1}{3^{s}}}-{\frac {1}{4^{s}}}+\cdots .$