Busy beaver shift function $BB(5)$
--MULLIGANACEOUS--, via Wikimedia Commons. Public domain.
The maximum number of steps made by a $5$-state, 2-symbol Turing machine that halts when started on a blank tape.
Value: $47176870$ (47,176,870)
Updates from the literature
-
1990-02
Lower bound: $47176870$
(47,176,870)
Marxen, H., & Buntrock, J. (1990). Attacking the busy beaver 5. Bulletin of the EATCS, 40, 247-251.
[via Sequence A060843 in the OEIS] -
2024-07-02
Upper bound: $47176870$
(47,176,870)
The bbchallenge Collaboration et al. Determination of the fifth Busy Beaver value. arXiv:2509.12337 (proof announced 2024-07-02).
[via Sequence A060843 in the OEIS]