Integral of Laguerre Polynomial

Question

Is there a general formula for integrals of the form $$ \int_0^{\infty}dr \ r^l e^{-a r} L^{n}_{m} (b r) $$ where $L^{n}_m$ is an associated Laguerre polynomial, $l \in \mathbb{Z}$, and $\text{Re }a > 0$? I found a formula here http://functions.wolfram.com/Polynomials/LaguerreL3/21/02/01/ however I did not understand the notation used (specifically the use of scubscripts on the coefficients in front of the sum). If someone knows the formula or could help me understand the one in the link above that would be very helpful!