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%I #11 Jul 11 2021 13:09:21
%S 2,6,30,146,42486,102966,597198,2847366,7998606,13133666,30478158,
%T 67622310,74476206,101258190,105161166,106364286,187605438,230000550,
%U 242915166,401913582,406756350,444314574,848205078,899715894,1508418054,1575220350,1578086334,1691859102
%N Numbers k such that 12^k == -1 (mod k-1).
%t Do[If[PowerMod[12, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Jun 09 2000
%E Terms a(14) onward from _Max Alekseyev_, Oct 12 2012