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%I #21 Aug 11 2014 22:45:24
%S 2,2,4,2,2,1,8,8,2,2,8,5,8,2,16,2,8,18,12,8,2,16,8,2,18,26,8,11,2,2,
%T 32,2,2,22,8,31,18,5,32,2,8,27,24,17,16,8,32,43,2,2,44,45,26,2,8,56,
%U 40,47,32,33,2,8,64,57,2,5,36,62,22,60,8,1,68,2,56,57,44,8,32,80,2,2,8,2,70
%N a(n) = smallest positive integer m such that 2^3^4^5^...^n == m (mod n).
%H Max Alekseyev, <a href="/A092188/b092188.txt">Table of n, a(n) for n = 2..1000</a>
%H R. Munafo, <a href="http://www.mrob.com/pub/math/seq-a092188.html">Smallest positive integer m such that 2^3^4^5^...^n == m mod n</a>
%F a(n) = n if n is a power of 2; otherwise a(n) = (2^3^4^5^...^n) mod n = A213013(n). [From _Max Alekseyev_, Jun 02 2012]
%e 2^3^4^5 = 2^3^1024. But 3 == -1 (mod 4), so 3^1024 == 1 (mod 4), so 2^3^1024 == 2^1 (mod 5) since 2^4 == 1 (mod 5). Thus a(5) = 2.
%K nonn,nice
%O 2,1
%A _N. J. A. Sloane_, following a suggestion of _J. H. Conway_, Apr 02 2004
%E More terms from _Robert Munafo_, Apr 11 2004
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