User blog comment:Tetramur/Well-defined Oblivion number (I think)/@comment-35470197-20200106221111/@comment-35470197-20200106230811

You can code any element in a fixed countable set into a word which includes precisely one sort of a symbol, and formal strings into a map whose values are such words. If you mind the formalisation of a map into formal strings, then you need two symbols.