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%I #3 Nov 11 2010 07:34:06
%S 0,3,3,3,992,3,3,3,877681,195496587,3,36787319437,1423919640546,
%T 3542630063906,77319946053101,6458069995222223,168313041233693968,3,
%U 139200566017647400916,207875641949796659481
%N Residues of 3^(2^p(n)-1) for Mersenne numbers with prime indices.
%C M_p is prime iff 3 ^ M_p is congruent to 3 mod M_p. Thus M_7 = 127 is prime because 3^127 mod 127 = 3 while M_11 = 2047 is composite because 3^2047 mod 2047 <> 3.
%H Dennis Martin, <a href="/A131462/b131462.txt">Table of n, a(n) for n = 1..100</a>
%F a(n) = 3^(2^p(n)-1) mod 2^p(n)-1
%e a(5) = 3^(2^11-1) mod 2^11-1 = 3^2047 mod 2047 = 992
%Y Cf. A095847, A001348, A131458, A131459, A131460, A131461, A131463.
%K nonn
%O 1,2
%A Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 20 2007
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