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%I #7 Nov 21 2013 12:50:02
%S 1,2,5,14,22,25,52,62,88,100,126,133,142,169,188,198,202,222,229,263,
%T 299,321,340,354,359,364,388,407,426,465,478,504,539,556,577,579,611,
%U 668,700,722,737,781,797,814,857,905,916,932,984,1033,1108,1118,1148
%N Numbers n such that semiprime(n)-1 is prime, where semiprime(n) is A001358.
%e a(1)=1 because semiprime(1)-1=3=prime, a(2)=2 because semiprime(2)-1=5=prime, a(3)=5 because semiprime(5)-1=13=prime.
%t nn=5000;With[{sps=Select[Range[nn],PrimeOmega[#]==2&]},Transpose[ Select[ Thread[ {sps,Range[ Length[sps]]}],PrimeQ[First[#]-1]&]][[2]]] (* _Harvey P. Dale_, Jul 19 2011 *)
%Y Cf. A174838.
%K nonn
%O 1,2
%A _Juri-Stepan Gerasimov_, Apr 11 2010
%E Corrected (478 inserted) by _R. J. Mathar_, Apr 13 2010
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