#if INTERACTIVE
#r "System.Drawing.dll"
#endif

open System.Drawing

let isSierpinskiCarpetPixelFilled(x, y) =
   let rec f (x,y) =
      if x > 0 || y > 0 then
         if x % 3 = 1 && y % 3 = 1 then false
         else f (x/3,y/3)
      else true
   f (x,y)

let width,height = 728, 728   
let image = new Bitmap(width, height)   
for y = 0 to height-1 do
   for x = 0 to width-1 do
      if isSierpinskiCarpetPixelFilled(x,y) 
      then image.SetPixel(x,y,Color.Black)
   
image.Save("carpet.png", Imaging.ImageFormat.Png)