Brjuno number in Pari-GP

[Ember Edison]

In folklore, Brjuno number period Shell-Thron-region base tetration is one of the most difficult tetration.

https://math.eretrandre.org/tetrationfor...43#pid9043

I found a Brjuno number implementation that is written in Maxima CAS. But I don't know Maxima CAS at all.
Can anyone rewrite it for Pari-GP?
https://commons.wikimedia.org/wiki/File:Brjuno_function.png?veaction=editsource§ion=3

[Ember Edison]

Oh, and I have a paper on Complex Brjuno functions for reference

https://arxiv.org/abs/math/9912018