The zeros of the Dirichlet's eta function $\eta(s)$ inside the critical strip match the non-trivial zeros of the Riemann zeta function $\zeta(s)$, as $\eta(s) = (1 - 2^{1-s}) \zeta(s)$.
What are the other known functions that give the same set of zeros of $\zeta(s)$ inside the critical strip?
EDIT:
I'm interested in functions given explicitly in series form:
$$\sum_{n = 1}^{\infty} f(n) \, n^{-s}$$