TheoremBase

Finite Powers of a Countable Set Are Countable

For a countable set S and a natural number k, the set of k-tuples in S, the maps from [k] to S, is countable.

Statement

In the setting of Routine Facts Used Without Citation: Arithmetic, Maps, Predicativity and Indices, let SS be a countable set and let k∈Nk\in\mathbb{N}, the set of natural numbers. Let Sk=S[k]S^{k}=S^{[k]} be the set of kk-tuples in SS, whose elements are the maps [k]→S[k]\to S by Tuples in a Set: the Set of n-Tuples and Their Components (ii).

SkS^{k} is countable.

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