TMBR: June 2026

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This edition of TMBR is in progress and has not yet been released. Please add any notes you think may be relevant (including in the form a of a TODO with a link to any relevant Discord discussion).

BB Adjacent

Busy Beaver for Lambda Calculus:

• TODO: BBλ(39) solved

SKI Calculus:

• New champions were discovered for Ξ₀(10), Ξ₀(13), Ξ₀(14), Ξ₀(15), Ξ₀(16), Ξ₀(17), Ξ₀(18) and Ξ₀(19). Ξ₀(10) was shown to be larger than Graham's number.
• New SK calculus champions were discovered for Ξ₀_SK(18) and Ξ₀_SK(26), showing Ξ₀_SK(26) to be larger than Graham's number.
• New BCKW system champions were discovered for Ξ₀_BCKW(7), Ξ₀_BCKW(8) and Ξ₀_BCKW(9).

Misc

• TODO: GPU deciders

Holdouts

• BB(6)
  • mxdys solved four TMs with FAR.^[1][2][3][4]
  • prurq solved another four TMs with FAR.^[5][6][7]
  • A TM was shown to be non-halting by hipparcos, which was later confirmed in Rocq by mxdys.
• BB(7)
  • Using new GPU based deciders, David SG reduced the number of remaining holdouts from 17,823,260 to 16,949,557, a 4.90% reduction.^[8]
  • Andrew Ducharme further reduced the amount of holdouts by 7.12% to 15,743,264 by running mxdys's FAR decider with various parameters.^[9]
• BB(2,6)
  • Andrew Ducharme reduced the number of holdouts from 413,513 to 412,086, a 0.35% reduction.^[10]
• BB(2,7)
  • Terry Ligocki enumerated 100K more subtasks, increasing the number of holdouts to 1,392,222,673. A total of 450K subtasks out of the 1 million subtasks (or 45%) have been enumerated.