Poisson distribution

https://doi.org/10.1351/goldbook.P04707
A discrete distribution with the differential @M03716@ of the form: \[f_{\text{w}}(x)=\frac{x}{a\,+\,1}=\frac{\text{e}^{-a}\ a^{x-1}}{(x\,-\,1)!}\] where \(x\) is a parameter characterizing the @C00956@, such as @R05271@ or @D01569@ and \(a\) is a positive adjustable parameter.
Source:
Purple Book, 1st ed., p. 56 [Terms]