Let $\rho$ denote a non-trivial zero of $\zeta(s)$ and $l_n(\rho)$ the $n$th coefficient in the Laurent expansion of $1/\zeta(s)$ about $\rho$. For example, if the pole is simple then we have $l_{-1}(\rho)=1/\zeta'(\rho)$.

My motivation is to understand the asymptotics of these sequences, the reasons for which I will briefly explain: Firstly, on intuitive grounds, these sequences encode the radii of convergence of the expansions at each $\rho$ and thus the vertical distribution of poles. However, I believe that a lot more can be said in connection with the horizontal distribution of zeros by considering the sequence $s:\mathbb{N}\rightarrow\mathbb{R}$, defined by $$s(n)=\sum_{\rho}\frac{l_{n}(1-\rho)}{\rho\zeta'(\rho)},$$ assuming all the poles are simple (one would have to modify $s(n)$ otherwise). The quantity $l$ in $$\frac{1}{l}=\limsup_{n\rightarrow\infty}\sqrt[n]{|s(n)|}$$(if it exists) is the radius of convergence of a certain power series, and measures twice the horizontal distance from the critical line to a zero of $\zeta(s)$ off the line, if any exist. Thus, establishing that $l>0$ establishes that there is a strip of non-zero width about the critical line containing no zeros off the line, and establishing that $l\geq 1$ is the Riemann Hypothesis. One might like to think of this as attacking the strip from the inside, rather than out.

I would be very interested to know if anything is known about $l_n(\rho)$, or indeed $s(n)$, and where I can find the details if so? If anyone would like me to explain how this series is derived, I will happily do so. Thanks!