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%I #20 Nov 21 2013 12:50:18
%S 15,26,34,35,38,55,57,69,74,85,87,91,94,95,106,118,119,123,134,161,
%T 185,202,206,209,213,215,217,221,254,259,265,295,298,303,309,314,321,
%U 334,339,346,362,365,371,377,381,382,393,395,398,407,415,417,437,445
%N Semiprimes p*q with p < q such that the concatenation p||q is again a product of two distinct primes.
%C A subsequence of A191913 and of A191911.
%H Harvey P. Dale, <a href="/A191915/b191915.txt">Table of n, a(n) for n = 1..1000</a>
%t okQ[n_]:=Module[{fd=FromDigits[Flatten[IntegerDigits/@ Transpose[ FactorInteger[ n]][[1]]]]},PrimeOmega[fd]==PrimeNu[fd]==2]; With[ {sps = Select[Range[500], PrimeOmega[#] == PrimeNu[#] == 2 &]}, Select[ sps, okQ]] (* _Harvey P. Dale_, Nov 22 2011 *)
%o (PARI) for(i=1, 500, is_A006881(i)|next; f=factor(i); is_A006881(eval(Str(f[1, 1], f[2, 1]))) & print1(i", "))
%K nonn,base
%O 1,1
%A _M. F. Hasler_, Jun 19 2011