F_n={1\over\sqrt5}(\alpha^n-\beta^n) where \alpha and \beta
are solutions of the quadratic equation x^2-x-1=0 and \alpha
> \beta is the explicit formula for the nth Fibonacci number
as given in this question.
The Golden Ratio is one of the roots of the quadratic equation and
this explains the many connections between Fibonacci numbers and
the Golden Ratio.