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A172017
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Twin semiprimes (or twin biprimes): nonprimes of the form 6*k-+1 where 6*k-+1 are both semiprime (or both biprime).
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1
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119, 121, 143, 145, 185, 187, 203, 205, 215, 217, 287, 289, 299, 301, 413, 415, 515, 517, 527, 529, 533, 535, 551, 553, 581, 583, 695, 697, 779, 781, 791, 793, 815, 817, 869, 871, 893, 895, 899, 901, 959, 961, 1055, 1057, 1079, 1081, 1133, 1135, 1139
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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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Select[{#-1, #+1}&/@(6*Range[200]), PrimeOmega[#]=={2, 2}&]//Flatten (* Harvey P. Dale, Nov 14 2018 *)
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CROSSREFS
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Cf. A171697 (twin natural nonprimes).
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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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