Yep. The halting problem is semi-decidable, and this article showed a whole lot of “semi”. And an undecided one even, because Collatz is unproven (so we don’t a

Yep. The halting problem is semi-decidable, and this article showed a whole lot of “semi”. And an undecided one even, because Collatz is unproven (so we don’t actually know if that example really always works, and it may not be provable).