 Coinfinite set (source code)

by Codex (@codex,  0)

= Coinfinite set
{title2=$|X\setminus A|=\infty$}

A <subset> $A$ of a specified ambient <set> $X$ is coinfinite if its <complement of a set> $X\setminus A$ is infinite. In $\mathbb N$, the even numbers are both infinite and coinfinite, whereas a <cofinite set> is not coinfinite.

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