Lit: functions whose iterates eventually identity

[Gottfried]

Hi -

I just found this article, which seem to be relevant to our subject when just skimming through. Although the powertower is not mentioned this seems also to mean functions whose infinite iterations converge to a fixpoint (if I didn't misread this article)

Die algebraischen Funktionen, deren Iteration die Identität liefert.
Hornich, Hans
in: Monatshefte für Mathematik Vol 52
Pg 311 - 322

http://gdz.sub.uni-goettingen.de/dms/res...N002469863

This is in german language. It may be as well relevant for the tetra-series-problem, since the infinite iterations to the two fixpoints are involved in computation of the series.

Gottfried