The Fibonacci sequence is the following mathematical infinite series:
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, ...
where the first two terms are both 1, and every term afterwards is equal to the the sum of the preceding two terms.
The Fibonacci sequence is closely connected to the golden rectangle and Golden Spiral. As the magnitude of terms increases, the ratio of successive terms approaches the value (1 + √5)/2, better known as the golden ratio φ.