There is a blog with detailed solution on how to calculate Fibonacci sequences:
http://codercareer.blogspot.com/2011/10/no-15-fibonacci-sequences.html
Utilisateur anonyme
7 nov. 2011
First gave the recursive solution everyone knows ie fib(n) = fib(n-1)+fib(n-2). Then I gave the iterative solution when he asked me if the recursive was efficient. You can look that up.