Let W be the set of Natural Numbers. What are all of the finite and co-finite subsets of W? It seems that all of the finite subsets of W will be inside of the power set of W, which we know will be uncountably infinite. But what is a co-finite subset of W?
I know that a co-finite subset is a subset whose complement is a finite set but am having trouble extending this definition to this question. For example, is X = {0, 1, 2} a co-finite subset of W?