Busy Beaver number $BB(6)$
The maximal number of steps that a $6$-state Turing machine can make on an initially blank tape before eventually halting.
Lower bound:
$7.4\times10^{36524}$
Upper bound:
Unknown
Updates
-
2011
Lower bound: $7.4\times10^{36524}$
Kropitz, P. (2011). Problém busy beaver.
[via The Busy Beaver Frontier, Scott Aaronson, 2020-09-29]