— Function: double gsl_sf_coupling_3j (int two_ja, int two_jb, int two_jc, int two_ma, int two_mb, int two_mc)
— Function: int gsl_sf_coupling_3j_e (int two_ja, int two_jb, int two_jc, int two_ma, int two_mb, int two_mc, gsl_sf_result * result)

These routines compute the Wigner 3-j coefficient,

          (ja jb jc
           ma mb mc)

where the arguments are given in half-integer units, ja = two_ja/2, ma = two_ma/2, etc.