pub fn bessel_k(n: u32, x: f64) -> Option<f64>Expand description
Modified Bessel function of the second kind K_n(x), integer order n ≥ 0. Requires
x > 0 → None otherwise. Order 1 via the Wronskian I_0 K_1 + I_1 K_0 = 1/x;
higher via K_{n+1} = (2n/x)K_n + K_{n-1}.