Set notation for infinite subsets.

Question

In set notation, how can one express an infinite set of subsets where each subset has exactly two elements $\{an-1, an+1\}$ where $a$ is a constant and $n\ge1$ and the $n$ value for each subset is one more than that of the previous subset. Example: $\{ \{a1-1, a1+1\},~\{a2-1, a2+1\},~\{a3-1, a3+1\},~. . . \}$

Answer 1

What about $\{\{an-1, an+1\}\ |\ n \in \mathbb{N}\setminus\{0\}\}$? Alternatively, for $n \in \mathbb{N}\setminus\{0\}$ you could define $A_n = \{an-1, an+1\}$ and the set you're interested in is $\{A_n\ |\ n \in \mathbb{N}\setminus\{0\}\}$.