— Function: double gsl_sf_bessel_Y0 (double x)
— Function: int gsl_sf_bessel_Y0_e (double x, gsl_sf_result * result)

These routines compute the irregular cylindrical Bessel function of zeroth order, Y_0(x), for x>0.

— Function: double gsl_sf_bessel_Y1 (double x)
— Function: int gsl_sf_bessel_Y1_e (double x, gsl_sf_result * result)

These routines compute the irregular cylindrical Bessel function of first order, Y_1(x), for x>0.

— Function: double gsl_sf_bessel_Yn (int n, double x)
— Function: int gsl_sf_bessel_Yn_e (int n, double x, gsl_sf_result * result)

These routines compute the irregular cylindrical Bessel function of order n, Y_n(x), for x>0.

— Function: int gsl_sf_bessel_Yn_array (int nmin, int nmax, double x, double result_array[])

This routine computes the values of the irregular cylindrical Bessel functions Y_n(x) for n from nmin to nmax inclusive, storing the results in the array result_array. The domain of the function is x>0. The values are computed using recurrence relations for efficiency, and therefore may differ slightly from the exact values.