Fibonacci numbers

Fibonacci numbers are a set of numbers defined recursively, each sequential number being the sum of the previous two: 0, 1, 1, 2, 3, 5, 8, ...


 * The greatest common divisor of any two Fibonacci numbers is also a Fibonacci number.
 * Any three consecutive Fibonacci numbers, taken two at a time, are relatively prime: gcd(Fn, Fn+1) = gcd(Fn, Fn+2) = 1

Resources

 * "The Man of Numbers: How Fibonacci Changed the World" by Maria Popova (brainpickings.org)