Test if a number is fibonacci

Question

I know how to make the list of the Fibonacci numbers, but i don\'t know how can i test if a given number belongs to the fibonacci list - one way that comes in mind is genera

Answer 1

Towards a solution, take a look at Binet's Formula.
(Look for "Closed-Form Expression" under Fibonacci Number on Wikipedia)

It says that the sequence of Fibonacci Number's is created by a simple closed formula:

I believe if you solve for n, and test if n is an integer, you'll have your answer.

Edit As @psmears points out, the same Wikipedia article also has a section on detecting Fibonacci numbers. Wikipedia is an excellent source.