Details

Most of the busy beaver values for and remain unreachable since they are noncomputable functions. The number of machines to explore (as well as their sizes) grows exponentially too fast. However, some values for a fixed-input empty tape and some small number of states and colors can be calculated.

The purple cells show the head position at each step. If either or appears with a sign, the Turing machine being displayed is only a busy beaver candidate. For a fixed (, ) size, if a busy beaver is known in (, ) it will be the first rule for the (, ) selection with the rest, if any, of the previous historical busy beaver candidates. If the busy beaver is unknown for that size space selection, then even the first rule will have a sign.