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.
f[x_]:=Sum[Sum[x-j,{j,i+1,x-1}],{i,0,x-1}]
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
