Fibonacci's Rabbits

Leonardo of Pisa, known as Fibonacci, introduced the sequence 1, 1, 2, 3, 5, 8, 13, 21, … to Europe in 1202 through a puzzle about breeding rabbits. Each number is the sum of the two before it. The ratio of consecutive Fibonacci numbers converges to the golden ratio φ ≈ 1.618. This same sequence appears in the spiral arrangements of sunflower seeds, pine cones, nautilus shells, and the branching of trees — apparently because it represents the most efficient packing arrangement in nature.