Let be a triangular area, and define to be obtained from by replacing each triangular area in with three similar and similarly oriented triangular areas each intersecting with each of the other two at exactly one vertex, each one half the linear scale of the original in size. The limiting set as (alternately the intersection of all these sets) is a Sierpinski gasket, also known as a Sierpinski triangle.

Figure: Sierpinski gasket stage 0, a single triangle, and at stage 1, three triangles

Figure: Stage 2, nine triangles, and stage , triangles