# Charlier polynomials

${\displaystyle C_{n}(x;\mu )={}_{2}F_{0}(-n,-x,-1/\mu )=(-1)^{n}n!L_{n}^{(-1-x)}\left(-{\frac {1}{\mu }}\right),\,}$
where ${\displaystyle L}$ are Laguerre polynomials. They satisfy the orthogonality relation
${\displaystyle \sum _{x=0}^{\infty }{\frac {\mu ^{x}}{x!}}C_{n}(x;\mu )C_{m}(x;\mu )=\mu ^{-n}e^{\mu }n!\delta _{nm},\quad \mu >0.}$