code: def window_blackman_harris(N):
      r
      a0 = 0.35875
      a1 = 0.48829
      a2 = 0.14128
      a3 = 0.01168
      return _coeff4(N, a0, a1, a2, a3)
docs: r"""Blackman Harris window
  
      :param N: window length
  
      .. math:: w(n) = a_0 - a_1 \cos\left(\frac{2\pi n}{N-1}\right)+ a_2 \cos\left(\frac{4\pi n}{N-1}\right)- a_3 \cos\left(\frac{6\pi n}{N-1}\right)
  
      =============== =========
      coeff            value
      =============== =========
      :math:`a_0`     0.35875
      :math:`a_1`     0.48829
      :math:`a_2`     0.14128
      :math:`a_3`     0.01168
      =============== =========
  
      .. plot::
          :width: 80%
          :include-source:
  
          from spectrum import window_visu
          window_visu(64, 'blackman_harris', mindB=-80)
  
      .. seealso:: :func:`spectrum.window.create_window`
      .. seealso:: :func:`create_window`, :class:`Window`