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*0.25^(n-3)*0.75), n=3 to +oo
sum (n*0.25^(n-3)*0.75), n=3 to +oo
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
