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a(n) = number at which the Ackermann function mod n stabilizes.
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%I #12 Dec 22 2016 22:05:53

%S 1,1,1,1,1,1,5,2,1,1,1,9,13,13,13,13,13,2,13,13,17,13,13,5,13,13,13,

%T 22,13,5,29,1,13,13,13,29,13,13,13,7,13,1,17,13,29,1,13,1,33,49,13,20,

%U 31,11,13,11,3,19,13,19,61,13,61,13,61,27,49,10,13,40,13,34,37

%N a(n) = number at which the Ackermann function mod n stabilizes.

%C a(1969) is undefined, but otherwise a(n) is defined for all n >= 2 and < 4000000.

%H J. Froemke and J. W. Grossman, <a href="http://www.jstor.org/stable/2323780">A mod-n Ackermann function, or what's so special about 1969?</a>, Amer. Math. Monthly, 100 (1993), 180-183.

%H J. W. Grossman, <a href="http://www.oakland.edu/~grossman/">Home page</a>

%K nonn

%O 2,7

%A _Jerrold Grossman_, Apr 25 2004