Hal,
Each of my recent fractal image set directories contains a short note. Here is the one in Set 17:
http://linuxenvy.com/bprentice/Fractals/Set%2017/ReadMe.html
This will lead you to the formula and parameter files and answer your questions.
Set 17 contains several other images that exhibit anti-bifurcation. For example 4c, 26a, 26b, 34, 40a, 40b and the one posted today 46.
Brian