The symbols of a sequence usually consist of lowercase a, b, c, d ... plus the right subscript n, m, etc. And the pronunciation is from left to right according to the pronunciation of English letters. When doing the problem, you may also encounter the capital letter a plus the subscript n, and the reading here is the same. A and a don't distinguish pronunciation. In order to distinguish, it can be pronounced as "big A" and "small A" respectively. I hope the above answers can help you solve the problem!