# Fibonacci numbers

The Fibonacci numbers, $F \colon \mathbb{Z} \rightarrow \mathbb{Z}$, is the solution of the following initial value problem: $$F(n+2)=F(n)+F(n+1), \quad F(0)=0, F(1)=1.$$ Often, $F(n)$ is written with a subscript: $F_n$.