It's a well known fact that the Schwartz class over integers defined by $$S(\mathbb{Z}^n)=\{\{a_m\}_{m\in\mathbb{Z^n}}\mid \sup_{m\in\mathbb{Z}^n}|m^\alpha a_m|<\infty, \forall \alpha\in\mathbb{N}^n\},$$ is a Frechet algebra. I've studied this in a Functional Analysis course in the past, now I'm just looking for a reference of this fact because I'd like to quote it on my master's thesis.
Any help would be appreciated.