Formulae for well formed formulae and their enumeration
Dov Tamari · Journal of the Australian Mathematical Society · 1974
1. General Idea. In this paper formal operators and bracketings devices are essentially the same; so are well formed formulae and correct bracketings. A well known theorem of symbolic logic (Post languages, etc.) and universal algebra characterizes well formed formulae among (linear) strings of symbols for variables and operators in terms of a system of numerical inequalities, one of them an equality.