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_{k=0}^{n} (k {{2n-k} choose n}\frac{1}{2}^{2n-k}), n=50.0
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
