 The latter series is an example of a Dirichlet series.When the real part of "s" is greater than 1, the Dirichlet series converges, and its sum is the Riemann zeta function "ζ"("s").On the other hand, the Dirichlet series diverges when the real part of "s" is less than or equal to 1, so, in particular, the series that results from setting "s" = –1 does not converge.