Is there a simple expression or approximation for the following series of exponential integrals:
$\sum_{k=1}^\infty E_1(k \nu)$
I believe this can be approximated by $\int_\nu^\infty E_1(x)/\nu \, dx$ for small enough $k$, but I'm interested in a closed form, or at least an estimate for the error from the approximation above.