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.
1/(n+1) * Sum[ (1 + (-1)^k )/2, {k, 0, n} ]
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
