Talk:Displaced Poisson distribution

I tried to implement the equation for the pmf in order to plot it. However, I wonder if the pmf equation is entirely correct. If r can take real values, then the meaning of the factorial expression is not well-defined.

I checked the original paper, where exactly the same equation is stated. It is not stated explicitly in the paper that r can be real-valued, but it is stated that s is the integral part of -r. So I suppose that r can be non-integer.

Is there an error in the original paper, or is my understanding of r wrong?

Kind regards Troels Pedersen