bessel_Y( n , z )

The Bessel function of the second kind of z in SageMath. A solution of the differential equation

$\frac{d^2 f}{dz^2} + \frac{1}{z} \frac{df}{dz} + \left[ 1 - \frac{n^2}{z^2} \right] f = 0$

The second linearly independent solution of this equation for integer order is bessel_J.

Plot on the real axis: