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.
i
n
f
n
=
0
s
i
n
4
0
n
!
p
i
2
4
1
Math Input
Natural Language
Math Input