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[ n^2/(4^(i - 1))^2 ] with i from 1 to floor(log(n)) + 1
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random