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A104243
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Semiprimes of the form prime(n) + prime(n+2) - prime(n+1).
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2
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4, 9, 15, 21, 25, 35, 39, 49, 55, 65, 69, 77, 85, 91, 93, 111, 123, 133, 141, 155, 161, 169, 183, 209, 215, 235, 247, 249, 265, 291, 309, 323, 327, 339, 341, 355, 361, 365, 377, 391, 393, 411, 437, 445, 451, 453, 505, 511, 515, 529, 551, 553, 565, 581, 583, 611
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Union[Select[First[#]+Last[#]-#[[2]]&/@Partition[Prime[Range[200]], 3, 1], PrimeOmega[ #]==2&]] (* Harvey P. Dale, Sep 11 2013 *)
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PROG
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(PARI) lista(nn) = {sps = Set(); for (n=1, nn, if (bigomega(sp=prime(n) + prime(n+2) - prime(n+1))==2, sps = Set(concat(sps, sp))); ); print(sps); } \\ Michel Marcus, Jun 03 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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