A fractal isn't a re-iterated formula at all... A fractal is a geometrical shape with scale-invariant self-similarity, a "broken" dimension - hence the name fractal. You can create some of the fractals be re-iterating something, a formula, a graphic process, ...
But the definition of a fractal can be found in Mandelbrot's books for example...

:rolleyes::sad:
Joy of Frax