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 A131409 Middle of three subsequent semiprimes with common prime factor = 3. 0
 3909, 87627, 132609, 163491, 167451, 170679, 209289, 224151, 270591, 309273, 318651, 327423, 340077, 395121, 444459, 481863, 497121, 522231, 536451, 584589, 624837, 633189, 680451, 752901, 765579, 767757, 830469, 848739, 878133, 915063, 938109, 953877, 954861 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS List of triples: {3903, 3909, 3921}, {87621, 87627, 87663}, {132603, 132609, 132621}, {163479, 163491, 163497}, {167439, 167451, 167457}, {170673, 170679, 170691}, {209283, 209289, 209301}, {224139, 224151, 224157}, {270573, 270591, 270597}, {309261, 309273, 309279}, {318639, 318651, 318657}, {327417, 327423, 327441}, {340071, 340077, 340089}, {395103, 395121, 395133}, {444453, 444459, 444471}, {481857, 481863, 481881}, {497109, 497121, 497127}, {522213, 522231, 522237}, {536439, 536451, 536457}, {584583, 584589, 584601}. LINKS PROG (PARI) lista(nn) = {vec = vector(nn, i, i); sp = select(i->(bigomega(i) == 2), vec); for (i = 2, #sp-1, if (gcd(sp[i-1], gcd(sp[i], sp[i+1])) == 3, print1(sp[i], ", ")); ); } \\ Michel Marcus, Oct 13 2013 CROSSREFS Sequence in context: A066386 A068240 A022212 * A209732 A221239 A136459 Adjacent sequences:  A131406 A131407 A131408 * A131410 A131411 A131412 KEYWORD nonn AUTHOR Zak Seidov, Oct 01 2007 EXTENSIONS Duplicated term 340077 removed and more terms added by Michel Marcus, Oct 13 2013 STATUS approved

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Last modified February 23 18:54 EST 2019. Contains 320438 sequences. (Running on oeis4.)