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### Regular Spherical Bessel Functions

Function: double gsl_sf_bessel_j0 (double x)
Function: int gsl_sf_bessel_j0_e (double x, gsl_sf_result * result)
These routines compute the regular spherical Bessel function of zeroth order, @math{j_0(x) = \sin(x)/x}.

Function: double gsl_sf_bessel_j1 (double x)
Function: int gsl_sf_bessel_j1_e (double x, gsl_sf_result * result)
These routines compute the regular spherical Bessel function of first order, @math{j_1(x) = (\sin(x)/x - \cos(x))/x}.

Function: double gsl_sf_bessel_j2 (double x)
Function: int gsl_sf_bessel_j2_e (double x, gsl_sf_result * result)
These routines compute the regular spherical Bessel function of second order, @math{j_2(x) = ((3/x^2 - 1)\sin(x) - 3\cos(x)/x)/x}.

Function: double gsl_sf_bessel_jl (int l, double x)
Function: int gsl_sf_bessel_jl_e (int l, double x, gsl_sf_result * result)
These routines compute the regular spherical Bessel function of order l, @math{j_l(x)}, for @c{$l \geq 0$} @math{l >= 0} and @c{$x \geq 0$} @math{x >= 0}.

Function: int gsl_sf_bessel_jl_array (int lmax, double x, double result_array[])
This routine computes the values of the regular spherical Bessel functions @math{j_l(x)} for @math{l} from 0 to lmax inclusive for @c{$lmax \geq 0$} @math{lmax >= 0} and @c{$x \geq 0$} @math{x >= 0}, storing the results in the array result_array. The values are computed using recurrence relations, for efficiency, and therefore may differ slightly from the exact values.

Function: int gsl_sf_bessel_jl_steed_array (int lmax, double x, double * jl_x_array)
This routine uses Steed's method to compute the values of the regular spherical Bessel functions @math{j_l(x)} for @math{l} from 0 to lmax inclusive for @c{$lmax \geq 0$} @math{lmax >= 0} and @c{$x \geq 0$} @math{x >= 0}, storing the results in the array result_array. The Steed/Barnett algorithm is described in Comp. Phys. Comm. 21, 297 (1981). Steed's method is more stable than the recurrence used in the other functions but is also slower.

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