The polygamma functions and the harmonic numbers in double precision, for the compilers, on the
interpreter's terms and by its algorithm: psi^(n)(z) for a whole n >= 0, reflected
left of Re z = 1/2 (DLMF 5.15.6), moved right by the recurrence (DLMF 5.15.5) and summed by the
asymptotic series (DLMF 5.11.2, 5.15.8); NaN at its poles 0, -1, -2, ... and at an order
that is not whole.
https://github.com/asc-community/AngouriMath/issues/2195