1RB0LB2LA_1LA0RC0LB_2RC2RB0LC

1RB0LB2LA_1LA0RC0LB_2RC2RB0LC (bbch) is the current BBB(3,3) champion. It was discovered in March 2025 by Nick Drozd and runs for $10\uparrow \uparrow 6$ steps before quasihalting.

Analysis by Shawn Ligocki

D(a, d) = 0^inf <C 0^a 1 2^d 1 0^inf

D(a, d+3) --> D(2^{a+6} - 2, d)
D(a, 0) --> Spin out
D(a, 1) --> C(14, a+1)
D(a, 2) --> C(14, a+4)

Start: D(14, 2)

This is actually a Collatz-like pentation-level TM that got unlucky! Each "reset" it iterates a tetration level function:

D(14, 3k+r) --> D(> 2^^k, r)

But in this case, the TM only resets once before spinning out:

D(14, 2) --> D(14, 18) --> Spin out

Source

https://nickdrozd.github.io/2025/03/24/bbb-3-3.html