Produce a graphical representation of a Sierpinski triangle of order N in any orientation.

An example of Sierpinski's triangle (order = 8) looks like this: 




 
#lang racket
(require 2htdp/image)
(define (sierpinski n)
  (if (zero? n)
    (triangle 2 'solid 'red)
    (let ([t (sierpinski (- n 1))])
      (freeze (above t (beside t t))))))
 