Holdouts lists

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A holdout (or undecided machine) is a Turing machine for which it is not known whether the machine halts or not from all-0 input tape. Holdouts are the machines which deciders are unable to decide.

Holdout lists are often shared by contributors:

BB space Date Shared by Number of holdouts File Notes
BB(6) July 6, 2024 @mxdys 7296 File:BB6 holdouts 7296.txt
BB(2,5) June 15th 2024 @dyuan01 273 File:2x5_holdouts_273.txt @Justin Blanchard's 499 holdouts minus machines solved by @mxdys
BB(6) June 13th 2024 @tjligocki 12,091 File:BB6 holdouts 12091.txt Work done with @Shawn Ligocki
BB(3,3) June 9th 2024 @Justin Blanchard 22 File:3x3.todo.txt, File:Mugshots small.pdf
BB(6) June 7th 2024 @mxdys 12,325 File:BB6 holdouts 12325.txt Some equivalent machines are removed.
BB(2,5) May 22nd 2024 @Justin Blanchard 499 File:2x5.todo.txt
BB(5) 0

Georgi Georgiev (Skelet) posted a list of 43 holdouts for BB(5) in 2003. bbchallenge.org successfully reduced the number of holdouts to zero in June 2024.