> (fibonacci 100) 354224848179261915075> (time (fibonacci 100)) 0.
> (time (fib 20)) 1.3000000000000114 (seconds)
> (time (fib 21)) 2.0670000000000073
> (time (fib 22)) 3.349999999999966
> (time (fib 23)) 5.5
> (time (fib 24)) 8.716000000000008
> (time (fib 25)) 14.25
(fib 100) would take over 2 billion years!