dont know what to do besides to just count. But i had a similar question before where i could se it was a rotation matrix and then it was easy. Is there an easy way for this one to?
I think FernandoRevilla's method and my proposed method boil down to the same thing (as they should!). The binomial theorem is going to give you those binomial coefficients that are showing up in the Jordan Normal Form power section of the wiki post.