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The Collatz Conjecture, also known as the 3n+1 conjecture, is a famous open problem named after Lothar Collatz.

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Is there a known Turing machine which halts if and only if the Collatz conjecture has a coun...

$\newcommand\PA{\mathit{PA}}$Let's note that this is not a question of whether Collatz is undecidable. The statement $\neg\mathrm{Con}(\PA)$ is undecidable (by $\PA$, assuming $PA$ is consistent) but …
Bjørn Kjos-Hanssen's user avatar