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.
T(x) = 1 + T(x-1) + T(x-2) + T(x-3)
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
