Thanks, I enjoyed that explanation quite a bit (didn't understand everything, but enough to get a major clue).
That's BB(10).
The naive way to solve this is to generate all possible 10 state state-machines and see what they produce - take the biggest one.
Except many of those will go into an infinite loop - and you cannot easily detect that (or detect it at all for arbitrary n - see also: halting problem) so you go into an infinite loop too.
Computation theory is fun.