5-state busy beaver winner

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The 5-state busy beaver champion (and winner!) is: https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA. It was found by Heiner Marxen and Jürgen Buntrock in 1989[1]. The machine halts after 47,176,870 steps and with 4098 1's on the tape, showing that BB(5)47,176,870 and Σ(5)4098.

This machine repeatedly applies the following map, starting with x=0[2]: g(x)5x+183if x0(mod3)g(x)5x+223if x1(mod3)g(x)HALTif x2(mod3)

The full orbit from x=0 is: 06163464114196334564946158426464416736612284HALT

  1. H. Marxen and J. Buntrock. Attacking the Busy Beaver 5. Bulletin of the EATCS, 40, pages 247-251, February 1990. https://turbotm.de/~heiner/BB/mabu90.html
  2. Aaronson, S. (2020). The Busy Beaver Frontier. Page 10-11. https://www.scottaaronson.com/papers/bb.pdf