def f (x,y,r,n,a=0):
   circle (x,y,r)
   r = r*0.5
   x2 = x + r*cos(a)
   y2 = y + r*sin(a)
   if n >0: f(x2 ,y2 ,r,n-1,a+PI)

f(150,150,100,5)