big-bullseye: number(n) -> image. Draw n concentric circles, alternating color beginning with black on the inside. Begin with a radius of 10 and increase the radius by 10 each successive circle.
sier-triangle: number(n) number(size) -> image. Make a Sierpinski triangle with n stages in the pattern and a side length of size. Do this by dividing the size in two when you make a smaller triangle, and arrange those triangles themselves in a triangle (see images).
