pub fn binom_dn<F: Float>(n: F, k: F) -> FExpand description
∂C(n, k)/∂n, the binomial coefficient’s slope in n. For a whole k from 0 to 64 it is the slope of the polynomial n(n - 1)…(n - k + 1)/k! by the product rule, within 2k ulps. Other arguments take C(n, k)(ψ(n + 1) - ψ(n - k + 1)), with the ψ difference in double words where both arguments are from 10 up, with the polynomial’s slope where a whole n below a whole k puts those ψ at a pole. Other poles of ψ give NaN.