code: def mgl_seq(x):
    
    odd_numbers = thub(count(start=1, step=2), 2)
    return Stream(1, -1) * x ** odd_numbers / odd_numbers
docs: Sequence whose sum is the Madhava-Gregory-Leibniz series.
  
      [x,  -x^3/3, x^5/5, -x^7/7, x^9/9, -x^11/11, ...]
  
    Returns
    -------
      An endless sequence that has the property
      ``atan(x) = sum(mgl_seq(x))``.
      Usually you would use the ``atan()`` function, not this one.