12.3 Recursively Enumerable Sets
12.3 Recursively Enumerable Sets A set is recursively enumerable if there is an algorithm that can list its elements. The older name is recursively enumerable , often abbreviated as r.e. The modern name is computably enumerable , often abbreviated as c.e. Both terms refer to the same idea. A set $A \subseteq \mathbb{N}$ is recursively enumerable if there is a Turing machine that prints exactly the elements of $A$: $$...