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%I #13 Jun 08 2015 02:25:33
%S 3,4,7,11,17,27,31,124,157,247
%N Number n such that A057137(n) is a semiprime.
%C First unknown: 397.
%e a(4) = 11 so A057137(11) = 12345678901 = 857 * 14405693 is a semiprime.
%Y Cf. A120819, A057137, A046461.
%K nonn,base
%O 1,1
%A _Eric Chen_, Dec 25 2014