Other orthogonal polynomials, Laguerre polynomials
They fulfil the orthogonality relation
\begin{equation*}
\int_{0}^{\infty}e^{-x}{\cal L}_n(x)^2dx=1,
\end{equation*}
and the recursion relation
\begin{equation*}
(n+1){\cal L}_{n+1}(x)=(2n+1-x){\cal L}_{n}(x)-n{\cal L}_{n-1}(x).
\end{equation*}