Task
Produce an ASCII representation of a Sierpinski triangle of order   N.



Example
The Sierpinski triangle of order   4   should look like this:

                       *
                      * *
                     *   *
                    * * * *
                   *       *
                  * *     * *
                 *   *   *   *
                * * * * * * * *
               *               *
              * *             * *
             *   *           *   *
            * * * *         * * * *
           *       *       *       *
          * *     * *     * *     * *
         *   *   *   *   *   *   *   *
        * * * * * * * * * * * * * * * *



Related tasks
 Sierpinski triangle/Graphical for graphics images of this pattern. 
 Sierpinski carpet


F sierpinski(n)
   V d = [String(‘*’)]
   L(i) 0 .< n
      V sp = ‘ ’ * (2 ^ i)
      d = d.map(x -> @sp‘’x‘’@sp) [+] d.map(x -> x‘ ’x)
   R d
 
print(sierpinski(4).join("\n"))