Poisson distribution

https://doi.org/10.1351/goldbook.P04707
A discrete distribution with the differential @[email protected] 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 @[email protected], such as @[email protected] or @[email protected] and \(a\) is a positive adjustable parameter.
Source:
Purple Book, 1st ed., p. 56 [Terms] [Book]