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 A124017 Numbers n for which 2n-1, 4n-1, 8n-1, 16n-1 and 32n-1 are primes. 7
 45, 90, 26820, 26925, 30705, 31710, 33375, 63420, 63570, 71805, 83865, 93075, 103185, 127140, 134025, 148050, 170460, 202635, 211035, 223305, 269505, 297225, 303660, 329175, 335625, 362505, 387975, 405270, 405405, 406425, 409755, 463335 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[15*Range[40000], And @@ PrimeQ /@ ({2, 4, 8, 16, 32}*# - 1) &] (* Ray Chandler, Nov 22 2006 *) Select[15*Range[31000], AllTrue[#*2^Range[5]-1, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Aug 05 2019 *) CROSSREFS Cf. A006254, A124485, A124493, A124494, A125113, A124514, A124515, A124516. Sequence in context: A115827 A070002 A101794 * A121925 A044183 A044564 Adjacent sequences: A124014 A124015 A124016 * A124018 A124019 A124020 KEYWORD nonn AUTHOR Artur Jasinski, Nov 04 2006 STATUS approved

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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)