Enumerating function of $a_n$ i.e. the function $\sum_{n=0}^{n=\infty}a_n x^n.$ [duplicate]

Consider the Fibonacci Series {$a_n$} defined by
$a_0=0,a_1=1,a_{n+1}=a_{n-1}+a_n$ for $n\ge1.$
Then what will be the enumerating function of $a_n$ i.e. the function $\sum_{n=0}^{n=\infty}a_n x^n.$