Here is the Mensa home page:
http://www.mensa.org/
There is an interesting association between the Fibonacci numbers and the golden section. This relationship is explored at this site:
https://www.mathsisfun.com/numbers/nature-golden-ratio-fibonacci.html
Here is a site which derives Binet’s formula (Problem 58):
http://mathforum.org/library/drmath/view/52677.html