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Numbers k such that 12^k + 1 is a semiprime.
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%I #5 Oct 17 2023 08:34:58

%S 2,4,5,11,16,32,109,128,193

%N Numbers k such that 12^k + 1 is a semiprime.

%e 11 is in this sequence because 12^11+1 = 13*57154490053 is a semiprime.

%Y Cf. A178248, A001358, A004064, A366582.

%K nonn,more

%O 1,1

%A _Sean A. Irvine_, Oct 16 2023