EDB — 16G

[16G] Given nonempty sets $I,A$, a sequence with indexes in $I$ and taking values in $A$ is a function $a:I\to A$; this though is usually written by the notation $(a_n{)}_{n\in I}$ . To denote the codomain, the notation $(a_n{)}_{n\in I}\subseteq A$ is also employed. In this text, in most cases, we will have that $I=\mathbb{N}$, and in this case we will simply write $(a_n)$.