The sequence that Leonardo discovered is one that has intrigued the minds of others. It's not a rule or theorem that one must follow when solving a problem. Instead, it's a noticeable sequence that can be applied in many ways throughout mathematics and in our lives. We see this sequence throughout nature, throughout the way that animals reproduce, and often found throughout architecture and golden triangles.
The sequence begins with the number 1. It has an order of adding the previous number to itself to make a pattern. For example: 0+a=a, a+a=b, a+b=c, and so on. So beginning with 1, and continuing the pattern, these numbers continue on forever. This number can also be considered a spiral that keeps on repeating such as the image below. This spiral is found very often in nature, such as in snail shells and starfish. This idea is also found throughout the diagonals of Pascal's Triangle.