Fibonacci sequence generator

Fibonacci sequence, also known as the golden section sequence or "rabbit sequence" due to its introduction by Leonardo da Vinci with rabbit breeding as an example. It refers to the series: 1, 1, 2, 3, 5, 8, 13, 21, 34, ... In mathematics, it is defined recursively: F(1)=1, F(2)=1, F(n)=F(n-1)+F(n-2)