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A157344
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Semiprimes that are the product of two distinct Sophie Germain primes.
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11
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6, 10, 15, 22, 33, 46, 55, 58, 69, 82, 87, 106, 115, 123, 145, 159, 166, 178, 205, 226, 249, 253, 262, 265, 267, 319, 339, 346, 358, 382, 393, 415, 445, 451, 466, 478, 502, 519, 537, 562, 565, 573, 583, 586, 655, 667, 699, 717, 718, 753, 838, 843, 862, 865
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OFFSET
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1,1
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COMMENTS
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6=2*3; 2 and 3 are Sophie Germain primes, 10=2*5; 2 and 5 are Sophie Germain primes, 15=3*5; 3 and 5 are Sophie Germain primes, ...
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LINKS
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MATHEMATICA
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lst={}; Do[If[Plus@@Last/@FactorInteger[n]==2, a=Length[First/@FactorInteger[n]]; If[a==2, b=First/@FactorInteger[n]; c=b[[1]]; d=b[[2]]; If[PrimeQ[2*c+1]&&PrimeQ[2*d+1], AppendTo[lst, n]]]], {n, 7!}]; lst
nn=100; With[{sgp=Select[Prime[Range[nn]], PrimeQ[2#+1]&]}, Take[ Union[ Select[ Times @@@ Subsets[sgp, {2}], PrimeOmega[#]==2&]], nn]] (* Harvey P. Dale, Nov 22 2012 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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