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(n) = -f(n - 2), f(1) = 1, f(2) = 2
f(n) = -f(n - 2), f(1) = 1, f(2) = 2
Natural Language
Math Input
Extended Keyboard