I'd love to see a numberphile episode on this, for two reasons: 1: it's been too long since we've had a Neil Sloane episode, which are always a highlight 2: i

I'd love to see a numberphile episode on this, for two reasons: 1: it's been too long since we've had a Neil Sloane episode, which are always a highlight 2: it sounds like the kind of thing where just a little bit more attention from maths enthusiasts will result in a proof of the sequence being finite (or not) very quickly