https://en.wikipedia.org/wiki/Steiner_chain
https://en.wikipedia.org/wiki/Inversive_geometry#Circle
https://en.wikipedia.org/wiki/Pappus_chain
https://en.wikipedia.org/wiki/Circle_packing_theorem
Fractals and Steiner chains
https://codegolf.stackexchange.com/questions/80152/recursive-steiner-chains