Fibonacci numbers

[druiaghtagh]

What are they and how do they work please?

[kempie]

http://en.wikipedia.org/wiki/Fibonacci_number

[taperface]

The above reference is pretty good, but as a simple example, after 2 start values (e.g., using 0 & 1 as the first 2 numbers), each number after that is the sum of the 2 preceding numbers, so......
0, 1 (0+1), 2, 3 (2 + 1), 5 (3+2), 8 (5+3), 13, 21,34,55,89,144,233,377,610,987...etc.
Sounds complicated, but you'll soon see how the pattern works.

[malagabob]

The numbers appear widely in the plant kingdom.In groups following the Fionacci formula

[New Judge]

And that's why you rarely, if ever, see a true four-leaf clover, because four is not a Fibonacci number.

[Physicsgirl]

if you get some squared paper and do a 1cm*1cm square, then another directly next to it (bear with me!), then use the long side of the rectangle you have created as the side length for a new square (2*2), use the long side again etc. this will give a pattern of squares. Starting in the 1*1 square, draw a 1/4 circle, continue this in each square and you'll get a nice spiral effect. Many painters used this to give "nice" proportions in their paintings, putting the main subject at the centre of the spiral. This is also to do wiith Fibonaccii.