Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
sum of binom (n,k) * binom (k,r) for k=a..n
sum of binom (n,k) * binom (k,r) for k=a..n
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
