I can read in your document:

(Cn Bn)i,k = 1 / (i + k + n +1)

it does not look complicated to calculate, or I did not understand well your Q...

Dear Professor

Thanks for your answer. As you can see I have computed the C^nB^n as you wrote, but I want to have an easier solution.

You may follow http://mathforum.org/library/drmath/view/73116.html

and for your future such problems and solution visit: https://www.khanacademy.org/math