The Busy Beaver Problem
A NEW MILLENNIUM ATTACK
Current Busy Beaver Statistics

Observed Statistics
Category B2 B3 B4 B5 B6
Candidate halters 6 80 2264 103095 6640133
Non-candidate halters 2 76 3844 271497 24911677
Tree Normalized
   ss transition 18 469 24425 1872797 189304589
   ss' transition 10 237 11428 806981 76717404
   First write 1 5 5 5 5 5
   First move right 4 5 5 5 5
   Empty tape 0 8 319 18527 1882827
Non-halters
   Back tracker 23 865 49481 4008364 403910416
   Subset loop 0 0 146 11013 2582783
   Simple loop 5 130 5605 381736 48492276
   Christmas tree 0 2 156 13987 2166668
   Alternating Christmas tree 0 0 23 2356 419598
   Leaning Christmas tree 0 0 0 69 23129
   3-Sweep Christmas tree 0 0 0 470 77740
   4-Sweep Christmas tree 0 0 0 76 17345
   5-Sweep Christmas tree 0 0 0 0 2156
   6-Sweep Christmas tree 0 0 0 0 1352
   7-Sweep Christmas tree 0 0 0 0 345
   8-Sweep Christmas tree 0 0 0 0 65
   Counter 0 0 0 113 25678
Holdouts 0 0 0 98 42166
Total 73 1877 97701 7491189 757218357
 

Representative Statistics
Category B2 B3 B4 B5 B6
Candidate halters 166 90207 103718908 206260328949 631450578198330
Non-candidate halters 18 15032 21405426 48677326680 163683442691930
Tree Normalized
   ss transition 1826 1429596 2141852028 5246088511050 19075918871435310
   ss' transition 330 266585 405653368 1002627681897 3667246872283790
   First write 1 3645 2599051 3693048057 8737080512391 30994415283203125
   First move right 324 257049 386201104 945571484025 3433227539062500
   Empty tape 0 2704 7859610 26709723432 123179236700000
Non-halters
   Back tracker 135 66745 72352399 138322654089 230363405036890
   Subset loop 0 0 67116 248518872 13058421488500
   Simple loop 117 99788 143484879 327997316304 1270875034985250
   Christmas tree 0 52 112200 287787024 1176689708500
   Alternating Christmas tree 0 0 2346 8485344 37454887500
   Leaning Christmas tree 0 0 0 95256 1552083000
   3-Sweep Christmas tree 0 0 0 236880 1562700000
   4-Sweep Christmas tree 0 0 0 38304 261123000
   5-Sweep Christmas tree 0 0 0 0 6756000
   6-Sweep Christmas tree 0 0 0 0 4056000
   7-Sweep Christmas tree 0 0 0 0 1035000
   8-Sweep Christmas tree 0 0 0 0 195000
   Counter 0 0 0 208152 7838415000
Holdouts 0 0 0 69552 719346000
Total = (4n + 1)2n 6561 4826809 6975757441 16679880978201 59604644775390625
Project Components
Tree Normalization
Non Halt Detection
Distributed Computing
Current Champions
n B(n) b(n) O(n) o(n)
1 1T 1T 1T 1T
2 2T 3T 2T 3T
3 3? 13R 3O 13R
4 5? 31R 8O 37R
5 11? 57R 15O 111O
6 25M 255M 239R 41606R
7 196M 13682M

8 672M 198339M


n P(n) p(n) R(n) r(n)
1 1T 2T 1T 2T
2 2T 4T 2T 4T
3 4R 14R 4R 14R
4 7R 32R 8R 38R
5 16R 112R 16R 112R
6 163R 27174R 240R 41607R

RSet by present RPI effort
MSet by Machado and Pereira
OSet by Oberschelp, et al.
TTrivial records
?Unknown origin

Also note: A solid yellow background indicates records have been explicitly confirmed by the present effort. A faded yellow indicates relative confidence but not yet an explicit proof.
Busy Beaver Research Team
Bram van Heuveln
Selmer Bringsjord
Boleslaw Szymanski
Carlos Varela
Kyle Ross
Owen Kellett
Shailesh Kelkar