[seqfan] Re: Binary Complement Sequences

[Tim Peters]

[Tom Duff]
> ...
> The number of steps for 425720 is at least 16,943,000,000 -- still running
> after 32 hours of CPU time on my M1 Mac Mini.

I gave up after 14 billion, because the size of integers in play
stopped obviously climbing after about 11 billion steps (I have trace
output showing this after every million steps).

So I have to consider the possibility that it fell into a cycle - in
which case my program would never end.

So I added simple code for cycle detection (Brent's method - much as
in his variation of Pollard's "rho" factorization method), and started
over.

Nothing yet to report, and possibly never.

Does your code detect a cycle if one occurs? Or does anyone have an
argument for why a cycle can't occur? (As Allen noted, every reachable
value has an infinite number of preimages, which intuitively seems to
me to boost the likelihood of a cycle.)

425720 is ... puzzling :-)