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: $10\uparrow \uparrow 15.60463<\mathrm{S}\mathrm{c}\mathrm{o}\mathrm{r}\mathrm{e}<\mathrm{R}\mathrm{u}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{m}\mathrm{e}<10\uparrow \uparrow 15.60466$.

It simulates the following Collatz-like rules, starting at $C(5)$, on tape configurations $C(n):=0^{\mathrm{\infty }}10^{n}110^5\text{C}\text{<mo>></mo>}{0}^{\mathrm{\infty }}$:

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