Choose challenge
Challenge goal
There remain 0 machines with 5 states to decide!! 🥳
We have reached our goal of proving "BB(5) = 47,176,870":
Here's what's next:
  • We are working on new busy beaver values such as BB(6) and setting new goals for these
  • We are maintaining busy beaver knowledge through our Discord, forum and wiki
·
What is this?
·
Visualization:
Machine
1LC1LE_---1LD_1RD0LD_1LA1RE_0LB0RC
Wiki entry: Skelet 1
Equivalent ID: #68,329,601
Status: Decided (Non Halt)
Decider: Coq-BB5 âž•
Machine code:
01
A 1LC1LE
B ---1LD
C 1RD0LD
D 1LA1RE
E 0LB0RC
Std format: 1LC1LE_---1LD_1RD0LD_1LA1RE_0LB0RC
Equivalent machine: 1RB1RD_1LC0RC_1RA1LD_0RE0LB_---1RC
Equivalent ID: 68329601
Copy code for https://turingmachine.io/
View at https://fiery.pages.dev/turing/
Change machine:
Random machine from the seed database
More options
From id in the seed database:
Zoology
This zoology is collaborative.
1. Cyclers
e.g: #279,081 #4,231,819 #4,239,083 
2. Translated cyclers
e.g: #59,645,887 #15,167,997 #59,090,563 #63,687,188 
3. Bouncers
e.g: #80,747,967 #88,427,177 #5,228,688 #5,608,043 
4. Exponential counters
e.g: #11,004,366 #10,936,909 #3,840,180 
5. Bells
e.g: #8,527,536 #73,261,028 #63,938,734 
Not classified yet:
e.g: #4,446,642 #7,410,754 #43,374,927 
Highlighted machines
Interesting machines:
· "inverted counter" [bbchallenge, 2023]
· "helix" [bbchallenge, 2023]
· "pointy wide" [bbchallenge, 2023]
· "chaotic" [Marxen & Buntrock, 1990]
· "complex counter" [Marxen & Buntrock, 1990]
· Machine #7,410,754
· Machine #2,977,651
· Machine #9,005,190
· Machine #43,374,927
· Machine #14,263,231
· Machine #36,909,813
BB champions and other halting machines:
· 2,133,492-halter [bbchallenge, 2021]
· 23,554,764-halter [bbchallenge, 2021]
· BB(5): 47,176,870-halter [Marxen & Buntrock, 1990]
· BB(6): >2↑↑↑5> 2\uparrow\uparrow\uparrow 5-halter [mxdys, 2025]
Some Skelet's machines:
· Skelet's machine 1 ≈ Machine #68,329,601
· Skelet's machine 17 ≈ Machine #1,365,166
· full list