The Feigenbaum Constants
Named after the mathematician Mitchell Feigenbaum.
Feigenbaum constants are two mathematical constants which both express ratios in a bifurcation diagram for a non-linear map.
δ = 4.669201609102990671853203821578…
The second Feigenbaum constant (sequence A006891 in the OEIS),
α = 2.502907875095892822283902873218…,
Used in chaos theory