In my exposure to mathematical literature, almost all sequences have values for which the term “countable” is inapplicable since they’re not sets. Even in the cases where the values themselves are sets, it was almost always used to mean a sequence with countable domain (i.e. length) and not one in which all elements of the codomain (values) are countable. It’s usually in the sense of “countably infinite” as opposed to “finite”, rather than opposed to “uncountably infinite”.
In my exposure to mathematical literature, almost all sequences have values for which the term “countable” is inapplicable since they’re not sets. Even in the cases where the values themselves are sets, it was almost always used to mean a sequence with countable domain (i.e. length) and not one in which all elements of the codomain (values) are countable. It’s usually in the sense of “countably infinite” as opposed to “finite”, rather than opposed to “uncountably infinite”.
ChatGPT is just bad at mathematical reasoning.