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A157342
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Semiprimes that are the product of two non-Sophie Germain primes.
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11
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49, 91, 119, 133, 169, 217, 221, 247, 259, 289, 301, 323, 329, 361, 403, 413, 427, 469, 481, 497, 511, 527, 553, 559, 589, 611, 629, 679, 703, 707, 721, 731, 749, 763, 767, 793, 799, 817, 871, 889, 893, 923, 949, 959, 961, 973, 1003, 1027, 1037, 1043, 1057
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 49=7*7;2*7+1=15(not Prime), 91=7*13;2*7+1=15(not Prime);2*13+1=27(not Prime), ...
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MATHEMATICA
| lst={}; Do[If[Plus@@Last/@FactorInteger[n]==2, a=First/@FactorInteger[n]; b=a[[1]]; k=0; If[Length[a]==2, c=a[[2]]; If[PrimeQ[2*c+1], k=1]]; If[ !PrimeQ[2*b+1]&&k==0, AppendTo[lst, n]]], {n, 7!}]; lst
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CROSSREFS
| Cf. A001358, A005384, A111206
Sequence in context: A093894 A158725 A090825 * A118886 A198773 A108164
Adjacent sequences: A157339 A157340 A157341 * A157343 A157344 A157345
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KEYWORD
| nonn
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AUTHOR
| Vladimir Orlovsky (4vladimir(AT)gmail.com), Feb 27 2009
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