sum pochhammer(1-a,n)/pochhammer(2-b,n)*gamma(n)/n!*(d/c)^n from n=1 to n=a-1

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.