Wigner3j( J123, M123) calculates the Wigner 3j-symbol according to Racah formula.
The Wigner 3j symbol is useful for multiplication of Spherical Harmonics (and their generalizations) and for addition of angular momentum.
The are related to the Clebsch-Gordan coefficients by:
Wigner3j( J123, M123 ) = <J1,J2,M1,M2| J1,J2,J3,-M3> * (-1)^(J1-J2-M3) * (2*J3+1)^(-1/2).
This function is not limited to the factorial limitation (170), so it can be useful for any value of J.