The nineteenth-century French mathematician Édouard Lucas (see Chapter H) investigated the numbers in the Fibonacci sequence (Fibonacci numbers) in great detail. There are both odd and even numbers in the sequence. To find the next number in the sequence merely add the previous two. The mathematical formula for this sequence is Fn = Fnl + Fn 2. For example,

and

Fibonacci numbers have intrigued mathematicians for centuries, mainly owing to the fact that they occur in a multitude of interesting and strange places, one of the strangest being biology. If you count seeds and petals in flowers such as sunflowers, daisies, pineapples and pine cones, you will find that the resulting numbers are all Fibonacci numbers.