0RB1LB_1LA1RB
0RB1LB_1LA1RB (bbch) is the Beeping Booping Busy Beaver champion for BBBB(2), pseudoquasihalting after 18 steps. This champion was rediscovered by Charlie Reams in October 2026, correcting an off-by-1 error in previous work by racheline.[1] It was discovered in September 2026 (though announced with little fanfare),[1] and proven to be the BBBB(2) champion by Crorem the following month.[2]
With boop transition A1 and beep transition A0, the machine boops at steps 6, 13, 18, ...; the first interval contains a single beep (therefore emitting a 1), and all later intervals contain no beeps (therefore emitting 0 infinitely thereafter). So, in the BBBB interpretation, it outputs an infinite stream of zeroes beyond this point, with the first zero being emitted at transition 18; thus, BBBB(M) = 18.