At least 3 times a week, someone on the r/Collatz sub-reddit says: "I came up with a proof for Collatz and had ChatGPT/Claude verify it and it thinks I'm a genius."

It's so common, the community barely comments on the absurdity of these posts any more.

This was a bit different, in that Lean was involved. That's more concerning.

(I'm told this actually wasn't found by looking for a proof for Collatz, just that Collatz was used to exhibit the bug, once found.)