The author of this formula is Helmut Senevald. This is an attempt to make Gaussian noise. If you average this noise, you will get the value of parameter A. You can change the dt and/or Ft. Based on this source, I made a new one, equal to the sum of similar sources with Ft parameters that are multiples of irrational numbers. After all, it is known that if you add up several random variables, the distribution of the sum will tend to be Gaussian. However, this increases the counting time.