The "cheta" function

[Gottfried]

My change of base formula relies on the following:
\( \lim_{k \to \infty} \log_a^{\circ k} \left( \exp_b^{\circ k} (x) \right) \).

just for the record; there was a discussion about this recently in sci.math. See Logarithm of repeated exponential Also an interesting msg of Robert Munafo, who used his "hypercalc" for a approximation with higher iterates.

Gottfried