The following result $$ \sum_{k=1}^\infty\left(\psi^{(1)} (k)\right)^2 = 3\zeta(3) $$ where $\psi^{(1)}$ is the polygamma function makes me think there is a nice sum for the series
$$ \sum_{k=1}^\infty \left(\psi^{(1)} (k+a)\right)^2 $$
or
$$ \sum_{k=1}^\infty \psi^{(1)} (k+a)\psi^{(1)} (k+b) $$
where $a$ and $b$ are any real numbers such that $a >-1, b>-1.$
Could you help me to find it?