BB(2,7)

The 2-state, 7-symbol Busy Beaver problem, BB(2,7), is unsolved. With Cryptids like Hydra in the preceding domain BB(2,5), we know that we must solve a Collatz-like problem in order to solve BB(2,7). The current BB(2,7) champion is simply inherited from BB(2,6) as BB(2,7) is just starting to be explored.

Top Halters

These are the 20 highest scoring machines that were found in the current investigation of BB(2,7). This list does not include TMs from smaller domains:

Phase 1

The initial phase of enumeration and reduction of holdouts started in November 2025 using C++ code mxdys shared. This work is ongoing and further described below. After this is completed, it is planned to run the Ligockis' "Enumerate.py" code to further reduce the number of holdout TMs.

Stage 1

The code provided by mxdys breaks up the BB(2,7) enumeration into 1 million subtasks which each run for about xxx minutes and leave ~xxx holdouts.

Stage 2

The Ligocki's "Enumerate.py" Python code is used to further reduce the number of holdouts and explore more of the TNF of BB(2,7).