Definition:Fibonacci Number

The Fibonacci numbers are a sequence which is formally defined recursively as:

$$F_0 = 0; F_1 = 1; F_n = F_{n-1} + F_{n-2}$$.

That is, the next number in the sequence is found by adding together the two previous ones.

We can see that the first few Fibonacci numbers are:

$$0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, \ldots$$