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 from r=0 to r=32 of ((2^7 choose r)((2^7-r) choose (64-2r)) (2^25 choose 2)^r (2^25)^(64-2r))/(2^32 choose 64)
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random