Lambert W
From specialfunctionswiki
The Lambert $W$ function is the (multi-valued) inverse of the function $f(x)=xe^{x}$.
Domain coloring of analytic continuation of branch $W_0(x)$ to $\mathbb{C}$.
Domain coloring of analytic continuation of branch $W_{-1}(x)$ to $\mathbb{C}$.
References
Having fun with the Lambert $W(x)$ function
Videos
6: Recursion, Infinite Tetrations and the Lambert W Function (4 August 2014)