prologues:=2;

def sierpinskiN (expr a, b, n) =
  if n = 0:
    draw a--(b rotatedabout(a,60))--b--cycle;
  else:
    sierpinskiN(a, 0.5[a,b], n-1);
    sierpinskiN(0.5[a,b], b, n-1);
    sierpinskiN(0.5[a,b rotatedabout(a,60)],0.5[a rotatedabout(b,-60),b], n-1);
  fi;
enddef;

beginfig(1);
  z0 = origin;
  z1 = z0 shifted (0,-500);
  sierpinskiN (z0, z1, 8);
endfig;

end