Compute the Wigner 3j symbol using the Racah formula.
W = Wigner3j( J123, M123 )
J123 = [J1, J2, J3], with the condition: Ji - Jj
<= Jk <= (Ji + Jj) (i,j,k are permutations of 1,2,3) M123 = [M1, M2, M3], with the conditions: Mi
<= Ji (i = 1,2,3) M1 + M2 + M3 = 0 All Ji and Mi have to be half integers (correspondingly).
Reference: Wigner 3j-Symbol entry of Eric Weinstein's Mathworld: http://mathworld.wolfram.com/Wigner3j-Symbol.html
Inspired by Wigner3j.m by David Terr, Raytheon, 6-17-04 (available at www.mathworks.com/matlabcentral/fileexchange).
By Kobi Kraus, Technion, 25-6-08.