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Search: id:A157345
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| A157345 |
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Numbers (semiprimes) that are the product of two distinct not-Sophie Germain primes. |
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+0
10
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| 91, 119, 133, 217, 221, 247, 259, 301, 323, 329, 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, 973, 1003, 1027, 1037, 1043, 1057, 1099, 1121, 1139, 1141
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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91=7*13 7 and 13 are not-Sophie Germain primes, ...
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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
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CROSSREFS
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Cf. A001358, A005384, A111206, A157342, A006881, A157344
Sequence in context: A020223 A161945 A140389 this_sequence A092125 A005935 A020307
Adjacent sequences: A157342 A157343 A157344 this_sequence A157346 A157347 A157348
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KEYWORD
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nonn
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AUTHOR
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Vladmir Orlovsky (4vladimir(AT)gmail.com), Feb 27 2009
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