Hi, I would be interested to know the machine config, and if it exists, any analysis of the halter found by the bbchallenge project which takes 23,554,764 steps.

The number of steps is reasonably close to half the step count of Marxen and Buntrock’s record-holder and I would like to know whether this machine is a variant on theirs using the same Collatz transformation, or if this is simply a coincidence.

Looks like it is also based on a Collatz transform 3k + a → 5k + c with 1 in 3 of the residues modulo 3 leading to halting. However, superficially it looks like it’s not the same transformation.

However, it seems to zig-zag at half the speed, and so it adds width quadratically at 1/sqrt(2) of the speed of the champion, and it finishes with used tape almost exactly half as long but with twice the density of 1s, for almost exactly the same number of 1s. So the numerical coincidence is still hard to dismiss without being able to say how weird collatz problems relate to other similar weird collatz problems.