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 A092125 Numbers n such that n, n+2, n+4 are semiprimes. 11
 91, 119, 141, 183, 201, 213, 215, 217, 287, 299, 301, 319, 391, 411, 413, 469, 515, 533, 579, 667, 685, 695, 789, 813, 1055, 1077, 1133, 1135, 1137, 1145, 1165, 1203, 1253, 1313, 1343, 1345, 1347, 1383, 1385, 1387, 1389, 1401, 1561, 1639, 1685, 1687, 1761 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Semiprimes in arithmetic progression. All terms are odd, see also A056809. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[Table[ #[[2]], {1}] & /@ FactorInteger[n]]; Select[ Range[ 1792], PrimeFactorExponentsAdded[ # ] == PrimeFactorExponentsAdded[ # + 2] == PrimeFactorExponentsAdded[ # + 4] == 2 &] (* Robert G. Wilson v, Feb 24 2004 *) SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 2000}], {1, _, 1, _, 1}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Feb 17 2020 *) PROG (MAGMA)IsSemiprime:=func< n| &+[ k[2]: k in Factorization(n) ] eq 2 >; [ n: n in [2..4300]|IsSemiprime(n) and IsSemiprime(n+2) and IsSemiprime(n+4)] // Vincenzo Librandi, Dec 16 2010 CROSSREFS Cf. A056809, A070552, A092126, A092127, A092128, A092129. Sequence in context: A140389 A236845 A157345 * A005935 A020307 A328662 Adjacent sequences:  A092122 A092123 A092124 * A092126 A092127 A092128 KEYWORD easy,nonn AUTHOR Zak Seidov, Feb 22 2004 STATUS approved

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Last modified October 21 11:51 EDT 2020. Contains 337914 sequences. (Running on oeis4.)