PS: the exact formula is fib(n) = 1/sqrt(5) * (0.5 + 0.5sqrt(5))^n - 1/sqrt(5) * (0.5 - 0.5sqrt(5))^n. If you round to integer anyway, the second term can be ignored as it is always <= 0.5.
You can simply write it as: round(phi^n/sqrt(5));
Check my example above :)
