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Dec 17, 2022 at 22:07 history edited Gro-Tsen CC BY-SA 4.0
fix (embarrassing) typo in question title
Dec 9, 2022 at 8:59 answer added Emil Jeřábek timeline score: 3
Dec 8, 2022 at 19:17 comment added Gro-Tsen @AlessandroCodenotti Indeed, and my first reaction when thinking about this was “how might it possibly give more than 7 different open sets when complement and closure only give 14?”, but, as you point out, the unions makes the problem different.
Dec 8, 2022 at 15:44 comment added Alessandro Codenotti This seems somewhat related to Kurstowski's complement-closure theorem, but that doesn't quite apply here because of the unions
Dec 8, 2022 at 15:26 history asked Gro-Tsen CC BY-SA 4.0