code: func Nuttall(L int) []float64 {
  	r := make([]float64, L)
  	LF := float64(L)
  	for i := 0; i < L; i++ {
  		iF := float64(i)
  		r[i] = 0.355768 - 0.487396*math.Cos((twoPi*iF)/(LF-1)) + 0.144232*math.Cos((fourPi*iF)/(LF-1)) - 0.012604*math.Cos((sixPi*iF)/(LF-1))
  	}
  
  	return r
  }
docs: // Nuttall generates a Blackman-Nutall window
  // See https://en.wikipedia.org/wiki/Window_function#Nuttall_window.2C_continuous_first_derivative