OFFSET
1,1
COMMENTS
This sequence is noncomputable, because it could be used to solve the halting problem. In fact, it is of the same degree of difficulty as the halting problem. - David Diamondstone (skeptical.scientist(AT)gmail.com), Dec 28 2007
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
J. P. Jones, Recursive undecidability - an exposition, Amer. Math. Monthly, 81 (1974), 724-738.
H. Marxen, Busy Beaver
Michael Somos, Busy Beaver Turing Machine
Michael Somos, Busy Beaver
CROSSREFS
KEYWORD
nonn,nice,hard,bref
AUTHOR
EXTENSIONS
More terms from David Diamondstone (skeptical.scientist(AT)gmail.com), Dec 28 2007
a(4) from Jonathan Lee, who enumerated all 25.6 billion 4-state machines up to 107 steps, Mar 05 2016
STATUS
approved