1RB0LD 1RC0RF 1LC1LA 0LE1RZ 1LF0RB 0RC0RE

1RB0LD_1RC0RF_1LC1LA_0LE1RZ_1LF0RB_0RC0RE (bbch) is a former BB(6) champion. It was discovered by Pavel Kropitz on 30 May 2022. This TM runs for over 10↑↑15 steps. An improved bound for this TMs runtime was achieved by Shawn Ligocki, using an extended version of tetration: $10\uparrow \uparrow 15.60463<Score<Runtime<10\uparrow \uparrow 15.60466$. See analysis: .

It simulates the following Collatz-like rules, starting at $C(5)$, on tape configurations $C(n)=0^{\infty }\;1\;0^{n}\;11\;0^{5}\;{\textrm {C>}}\;0^{\infty }$:

$${\begin{array}{l}C(4k)&\to &Halt({\frac {3^{k+3}-11}{2}})\\C(4k+1)&\to &C({\frac {3^{k+3}-11}{2}})\\C(4k+2)&\to &C({\frac {3^{k+3}-11}{2}})\\C(4k+3)&\to &C({\frac {3^{k+3}+1}{2}})\\\end{array}}$$