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1992-09-20
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# From: heim@tub.UUCP (Heiner Marxen)
# Newsgroups: sci.math
# Subject: busy beaver Turing machine
# Date: 24 Aug 89 13:24:10 GMT
# Organization: Technical University of Berlin, Germany
#
# This is about ``busy beavers'' (is there a more appropriate newsgroup?).
# Unfortunately I did read this newsgroup only sporadically, and don't know
# whether this has been discussed already. My other sources of information
# (mainly the German issue of `Scientific American') don't tell me more.
#
# As far as I know the 5-state busy beaver question is not yet settled.
# With the help of a program I have found a 5-state Turing machine which
# halts (after 11,798,826 steps) and produces 4098 ones on the tape, namely
# A0 -> B1L A1 -> A1L // `A' is the initial state
# B0 -> C1R B1 -> B1R // `R' is `move right'
# C0 -> A1L C1 -> D1R // `L' is `move left'
# D0 -> A1L D1 -> E1R
# E0 -> H1R E1 -> C0R // `H' is the halting state
# The best machine I knew before produces 1915 ones (published in 1985
# by Scientific American, I believe). My questions are
# Q1: Is there ongoing (or completed) research ? Any (theoretic) results ?
# Q2: Are there any better 5-state machines known or published ?
# Q3: Who else studies the busy beaver problem with general purpose computers?
#
# Answers to the above, hints and pointers are welcome.
# Please answer by e-mail; if appropriate I will summarize to the net.
# = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
# Heiner Marxen, from europe: unido!tub!heim
# from world: pyramid!tub!heim
# bitnet: heim%tub.BITNET@mitvma.MIT.EDU
1. 1l2 1l1
2. 1r3 1r2
3. 1l1 1r4
4. 1l1 1r5
5. 1h0 0r3