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%I #4 Mar 31 2012 13:21:55
%S 2,3,2,3,11,5,13,3,17,11,23,5,53,13,11,7,67,17,37,11,13,23,47,5,101,
%T 53,53,13,59,11,61,17,23,67,29,17,73,37,53,11,83,13,173,23,19,47,281,
%U 7,97,101,67,53,107,53,89,13,37,59,353,11,367,61,71,31,79,23,269,67,47,29
%N First prime such that p^2==1 (mod n).
%e a(2)=3 because 3^2=9==1 (mod 2), while 2^2==0 (mod 2).
%o (PARI) for (n=1,100, forprime(p=2,1000,if ((p^2-1)%n==0,print1(p","); break)))
%K nonn
%O 1,1
%A _Jon Perry_, Nov 21 2002