computes the Wigner 6-j coefficient,
{ja jb jc jd je jf}
where the arguments are given in half-integer units,
ja = two_ja/2
, jd = two_jd/2
, etc.
err contains an estimate of the absolute error in the value z.
This function is from the GNU Scientific Library, see http://www.gnu.org/software/gsl/ for documentation.
Package: gsl