BB(2,5): Revision history

18 September 2026

• curprev 10:1110:11, 18 September 2026 Yves30. talk contribs 24,273 bytes −92 Remove the last ranked TM in the top 20 halting list after having added a new TM Tag: Visual edit
• curprev 10:0510:05, 18 September 2026 Yves30. talk contribs 24,365 bytes −2 Minor change: 1.589e20 to 1.6e20 for the nb of steps of a halting TM (lower the number of significative digits when comparing it to 2 other halting TMs of the same category, one of them being given only a lower bound) Tag: Visual edit
• curprev 09:5909:59, 18 September 2026 Yves30. talk contribs 24,367 bytes +175 Add a Rocq-proved halting TM in the halting list with a lower bound and a note that the precise info of nb of steps is yet to be given ; add "probviously halting potential cryptid" to the champion contender in the list. Tag: Visual edit

16 September 2026

• curprev 04:5504:55, 16 September 2026 C1 talk contribs 24,192 bytes +36 Synchronized a more precise lower bound for the runtime of the current BB(2,5) champion.

15 September 2026

• curprev 14:1214:12, 15 September 2026 Sligocki talk contribs m 24,156 bytes +1 →Top Halters: Move ref Tag: Visual edit

14 September 2026

• curprev 21:4621:46, 14 September 2026 ADucharme talk contribs 24,155 bytes +300 formally solved TMs in "Solved with moderate rigor" category moved to "Formally proven," links to mxdys's announcement included. Tag: Visual edit
• curprev 14:5514:55, 14 September 2026 Yves30. talk contribs 23,855 bytes +15 Reformulation of "holdouts" section introduction in order to avoid repetitions vs the "certified progress" section Tag: Visual edit
• curprev 14:4514:45, 14 September 2026 Yves30. talk contribs 23,840 bytes +310 Update of the proof status: the number of holdouts is now 60, all others TMs have been proven in Rocq, especially the 5 "solved with moderate rigor" ones. However, the full list based on previous 83 is conserved with precisions/annotations when necessary Tag: Visual edit
• curprev 12:1212:12, 14 September 2026 Yves30. talk contribs 23,530 bytes 0 For current champion and 3rd halter change the notation for number of steps until halting from S (capital) to s, according to the notation conventions in the field. Capital S is for the BB value only, thus S >= s(current champion) Tag: Visual edit
• curprev 09:3409:34, 14 September 2026 Yves30. talk contribs 23,530 bytes 0 Correct erratum Tag: Visual edit
• curprev 09:3309:33, 14 September 2026 Yves30. talk contribs 23,530 bytes +71 Precisions on champion and 3rd ranked halter S scores in the "formally proven" section Tag: Visual edit
• curprev 09:2409:24, 14 September 2026 Yves30. talk contribs 23,459 bytes +88 Add link to Rocq proof of 3rd ranked halter found in 2025 Tag: Visual edit
• curprev 09:1409:14, 14 September 2026 Yves30. talk contribs 23,371 bytes −28 Order all the top halters by S (number of steps until halting). The TM originally ranked 4th has a sigma score of 8.3e466, and the Rocq proof on discord mentioned a quadratic machine (S ~ sigma²). Therefore this machine ranks 3rd and has a S of 6.9e933 Tag: Visual edit
• curprev 08:0508:05, 14 September 2026 ADucharme talk contribs 23,399 bytes −421 →Certified progress: proposed rewrite Tag: Visual edit

13 September 2026

• curprev 22:4022:40, 13 September 2026 Yves30. talk contribs 23,820 bytes +32 Re-reading the discord discussion on it, the estimated chance for the probviously halting tetrational overflow counter to surpass the champion is between 25 and 50%, since the halting probability per overflow is estimated between 0.2 and 0.35 and 3 nonhalting overflows are required. Thus the previous single value of 30% is inappropriate. Tag: Visual edit
• curprev 21:5421:54, 13 September 2026 Yves30. talk contribs 23,788 bytes 0 Coherence of the info on probviously halting contender: 30% chance to surpass the champion is the up-to-date estimate. The correct info is mentioned below on the line specific to the TM in the general list. The 1/8 figure mentioned at the beginning is an earlier estimate, obsolete. Tag: Visual edit

5 August 2026

• curprev 21:2221:22, 5 August 2026 C7X talk contribs 23,788 bytes +26 Link abbreviation

2 June 2026

• curprev 08:0108:01, 2 June 2026 RobinCodes talk contribs 23,762 bytes +666 Add BB(2,5) progress Tag: Visual edit

24 April 2026

• curprev 17:4417:44, 24 April 2026 Polygon talk contribs 23,096 bytes −20 Undo revision 7264 by Polygon (talk) link went to a relevant channel, so not wrong Tag: Undo
• curprev 15:4415:44, 24 April 2026 Polygon talk contribs m 23,116 bytes +20 →Cryptids: fixed wrong link

19 April 2026

• curprev 09:3009:30, 19 April 2026 Polygon talk contribs m 23,096 bytes −8 credit
• curprev 09:2909:29, 19 April 2026 Polygon talk contribs 23,104 bytes +7 →Top Halters: added another missing top halter
• curprev 09:2509:25, 19 April 2026 Polygon talk contribs 23,097 bytes −100 →Top Halters: added some missing halters from 2024

13 April 2026

• curprev 16:2616:26, 13 April 2026 Polygon talk contribs 23,197 bytes +40 →Top Halters: fixed credits for two new top 20 halters
• curprev 16:2416:24, 13 April 2026 Polygon talk contribs 23,157 bytes +274 →Solved with moderate rigor: added simulation until halt
• curprev 15:3515:35, 13 April 2026 Polygon talk contribs 22,883 bytes −30 →Top Halters: added two new top halters

10 April 2026

• curprev 09:1809:18, 10 April 2026 RobinCodes talk contribs 22,913 bytes +122 →Holdouts: Added dyuan's progress Tag: Visual edit

9 April 2026

• curprev 19:3419:34, 9 April 2026 RobinCodes talk contribs 22,791 bytes +244 →Unsolved: Added all progress. Tag: Visual edit

2 April 2026

• curprev 21:4421:44, 2 April 2026 RobinCodes talk contribs 22,547 bytes +122 →Unsolved: Added long. analysis by dyuan Tag: Visual edit
• curprev 14:1214:12, 2 April 2026 RobinCodes talk contribs 22,425 bytes +523 →Certified progress: Updated progress Tag: Visual edit

1 April 2026

• curprev 14:5214:52, 1 April 2026 RobinCodes talk contribs 21,902 bytes +30 →Certified progress: Fix Aristotle Links Tag: Visual edit
• curprev 14:4314:43, 1 April 2026 RobinCodes talk contribs 21,872 bytes +1,740 →Certified progress: Added new mxdys formalisation and missed older mxdys formalisation Tag: Visual edit
• curprev 14:2314:23, 1 April 2026 RobinCodes talk contribs m 20,132 bytes −2 →Solved with moderate rigor: Removed random comma Tag: Visual edit
• curprev 09:1309:13, 1 April 2026 RobinCodes talk contribs 20,134 bytes +5 →Holdouts Tag: Visual edit

16 March 2026

• curprev 16:1316:13, 16 March 2026 ADucharme talk contribs 20,129 bytes +240 →Holdouts: move 2 formally solved TMs out of informal proof section Tag: Visual edit

11 March 2026

• curprev 17:2617:26, 11 March 2026 ADucharme talk contribs 19,889 bytes +663 →Holdouts: new TM solved+verified 3/11/26 Tag: Visual edit

6 March 2026

• curprev 21:3421:34, 6 March 2026 RobinCodes talk contribs 19,226 bytes +586 →Unsolved: Added simulation results by prurq Tag: Visual edit

18 February 2026

• curprev 11:2611:26, 18 February 2026 Polygon talk contribs 18,640 bytes +20 →Top Halters: Added new (old) top halter

15 February 2026

• curprev 18:3718:37, 15 February 2026 RobinCodes talk contribs 18,620 bytes +130 →Holdouts: Added info for a holdout (new by Peacemaker) Tag: Visual edit

12 February 2026

• curprev 19:4219:42, 12 February 2026 RobinCodes talk contribs 18,490 bytes +939 →Holdouts: Added BB(2,5) progress Tag: Visual edit

2 February 2026

• curprev 17:5517:55, 2 February 2026 RobinCodes talk contribs 17,551 bytes 0 →Certified progress: Fixed informal holdout count Tag: Visual edit
• curprev 17:5417:54, 2 February 2026 RobinCodes talk contribs 17,551 bytes +415 →Certified progress: Extended the section with a paragraph about new progress Tag: Visual edit

29 January 2026

• curprev 07:5707:57, 29 January 2026 ADucharme talk contribs 17,136 bytes +290 →Holdouts: moved newly solved TM to Formal proof section, updated date of last change at top of list Tag: Visual edit

27 December 2025

• curprev 13:5513:55, 27 December 2025 Polygon talk contribs 16,846 bytes +1,936 →Top Halters: expanded list to top 20

16 December 2025

• curprev 18:1818:18, 16 December 2025 RobinCodes talk contribs 14,910 bytes +106 →Holdouts: Added mxdys's notes to a machine Tag: Visual edit
• curprev 18:1518:15, 16 December 2025 RobinCodes talk contribs 14,804 bytes +514 →Holdouts: Added information to four machines Tag: Visual edit

14 December 2025

• curprev 14:3514:35, 14 December 2025 RobinCodes talk contribs 14,290 bytes +104 →Unsolved: Added all data from spreadsheet Tag: Visual edit
• curprev 14:3314:33, 14 December 2025 RobinCodes talk contribs 14,186 bytes +122 →Unsolved: Added more data from spreadsheet Tag: Visual edit
• curprev 14:3214:32, 14 December 2025 RobinCodes talk contribs 14,064 bytes +155 →Unsolved: Added data from spreadsheet Tag: Visual edit

10 November 2025

• curprev 19:5919:59, 10 November 2025 Sligocki talk contribs 13,909 bytes +92 →Cryptids: Add 1/8 champ Tag: Visual edit