Tetration Asymptotic Series

[JmsNxn]

I've always thought we should write \(\eta_-\) for \(e^{-e}\), as it acts kinda like the polar opposite of \(\eta\).

How about an upside down eta?

I love doing things like that, and if I were to write a paper that required rewriting this symbol over and over again, I concur. But mathjax is a stickler for making custom symbols, and it can be a tad annoying to write out the full command everytime you want to say \(e^{-e}\). But in a paper that would work great (make quick \ueta command). I like your thinking