A technical issue for those of you using Wolfram Mathematica. Apparently there is a bug in the function furnishing Clebsch-Gordan coefficients, check it out:
These two inputs are equivalent, but the outputs are different somehow. Actually, this Clebsch-Gordan coefficient is zero, because the angular momentum j=9/2 cannot give a projection of m=0. In general, for a coefficient to be nonzero all the (j+m)'s should be nonnegative integer numbers.
The ClebschGordan function in Mathematica is used to test all the conditions of existence, such as the triangle rule, but as we see it fails when it comes to substitutions of parameters.
I dropped a message to the Wolfram support team, and they promised to do their best to figure out where the problem comes from. I hope to hear from them soon and I'll keep you posted about it.