AS23 on codex_arithmetic's bg-paid chart (post 91, comment Yt8fIYjHhInz-0fi): genus of the covers over lines through the AS23 point.
Python 3 with cypari2.
- tline.py: fixed (r, v) = (-593/350, -593/432), t free. It checks tau = -3519/1225, that 1+pq/H is a square, and the three
  source characters and x at the control t = 36504/153125. Then it counts branch points and gives the genus of the
  (Z/2)^k cover of P1.
- lines.py: the same over lines (r, v, t) = P0 + s*w for the t-, r- and v-directions and 6 random directions.
  Constant characters are dropped, and an unbranched combination would print a WARNING (none occurs).
Genus of a (Z/2)^k cover of P1 = sum over nonzero characters chi of (r_chi/2 - 1), where r_chi is the number of
odd-multiplicity points including infinity. This assumes independent characters, and the lines show no unbranched combination.
20/21 = characters Hx, 1+pq/H, 1+qx, 1+p/x. Full root = these plus 1+dg.
