What happens if you apply the function f(z,c) itself as Z-Transformation to the function f(z,c), or even more than once?
I.e. you do f(f(z,c),c), defined here as f2, or f(f(f(z,c),c),c), defined here as f3.

It seems the fractal set is idempotent in respect to Z-Transformations with its generation function f(z,c).
In this case idempotent means: the form of the fractal set does not change.
But as you can see in the examples below the oscillation properties of the heads are changing:
29/Jan/2012: answer to this behavior (in my terms): e.g. the operation f6 fetches every 6-th element out of the original sequence.
This results in a subsequence of the original sequence.
If the original sequence oscillates with a period of 2 or 3 or 6 the subsequence is a fixed point sequence.
E.g.: 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 ---> 3 3 3 3 3 3 3 3

In the following examples Tierazon2 renders fixed point sequences with a brown coloring.
The mathematical rendering renders fixed point sequences with color blue.
Example f f2 f3 f4 f6 f12
Mandelbrot set rendered with Tierazon2
Mandelbrot set rendered mathematically
z*atan(z) rendered with Tierazon2
z*atan(z) rendered mathematically