This question is mainly about the clarification of the terminology BB(n), not how busy beavers work. It seems common to refer to busy beaver numbers like BB(2) assuming 2 is the number of states. Do we also assume 2 input symbols? Further, is the result of BB(2) referring to the count of ones printed or the count of steps?

Simply put, what is BB(2)? 6, 4, BB(2,m), a bound, etc?

  • $\begingroup$ This is answered in papers and websites on the problem. Have you looked for any? $\endgroup$ Commented Nov 14, 2021 at 23:13
  • $\begingroup$ @YuvalFilmus oh yes -- I've seen n-state/1-symbol/2-symbol, m=n symbol... seems to be some noise. I think Wikipedia had n-state/2-symbol. $\endgroup$ Commented Nov 15, 2021 at 4:00
  • $\begingroup$ There might be more than one common definition, or to state it differently, it is the concept that matters rather than the details. $\endgroup$ Commented Nov 15, 2021 at 4:36


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