const SINGULAR_REACH: f64 = 3.0;
Largest 2 (ν₀ + 1/2) √s ≈ (ν₀ + 1/2) θ at which the logarithmic series is summed.
2 (ν₀ + 1/2) √s ≈ (ν₀ + 1/2) θ