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.
summation%281%2Fk**2%2C %28k%2C 1%2C oo%29%29
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random