jaxpolylog.polylogs._zero_branch_coeffs

_zero_branch_coeffs(s: int, P: int) → tuple

Precompute c[k] = ζ(s-k) / k! for k = 0..P-1.

Branch table:

• arg = s-k ≥ 2: ζ(arg) via _zeta_pos_int().

• arg = 1 (k = s-1): coefficient set to 0 (cancels the explicit log(-μ) term in jax_polylog()).

• arg = 0 (k = s): ζ(0) = -1/2.

• arg < 0, n = 1 - arg:

  • n odd ≥ 3: B_n = 0 → coefficient = 0.

  • n = 2m even: coefficient = -B_{2m}/(2m · k!) as an exact Fraction, then floated. Never materialises B_{2m} or k! separately.