Here is the Mensa home page:

http://www.mensa.org/

Some practice with sequences and summation notation (which we introduce in the next section) can be found at this site:

http://www.richland.cc.il.us/james/lecture/m116/sequences/sequences.html

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