\begin{definition}[Definition:Fibonacci Number]
The '''Fibonacci numbers''' are a sequence $\sequence {F_n}$ of integers which is formally defined recursively as:
:$F_n = \begin {cases} 0 & : n = 0 \\
1 & : n = 1 \\
F_{n - 1} + F_{n - 2} & : \text {otherwise} \end {cases}$
for all $n \in \Z_{\ge 0}$.
That is, the next integer in the sequence is found by adding together the two previous ones.
\end{definition}