[throwaway15289]

Draw a triangle and put 4 shrunk copies of itself in the triangle (center one flipped)?

http://imgur.com/m0Okt see components on rhs.

Edit: Oh sorry, was confused about which one Sierpinski's was. Can fix it by omitting middle triangle: http://imgur.com/MVmPh

[bryogenic]

Or you can do the inverse http://i.imgur.com/tMbrj.png