$\delta$ and $\alpha$ are the first and second Feigenbaum constants [6][3]. $b$, $c$, $d$, $\kappa$ are additional Feigenbaum constants considered by Broadhurst [2].
How they were obtained: Transcribed from the literature rather than computed here. The Feigenbaum constants have been established rigorously in the literature by computer-assisted proof, but nothing in this table connects these digits to that work.
