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 A337858 Integers k>=3 such that 2^k == 2 (mod k*(k-1)*(k-2)/6). 1
 3, 5, 37, 101, 44101, 3766141, 8122501, 18671941, 35772661, 36969661, 208168381, 425420101, 725862061, 778003381, 818423101, 1269342901, 9049716901, 27221068981, 60138957061, 125980182901, 137330493301, 314912454781, 315322826869, 478543291381, 667933881301 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Computed terms are prime. Is it always the case? If not it would be interesting to compute the smallest pseudoprime. It seems that all larger terms are of the form 180*k + 1, starting at a(5) = 44101 = 180*245 + 1. - Hugo Pfoertner, Sep 27 2020 Other terms of the form 180*k+1 (which are all prime): 60138957061, 125980182901, 137330493301, 478543291381, 667933881301, 700212813301, 701030830501, 720023604301, 766514618101, 778382658901. - Chai Wah Wu, Oct 06 2020 LINKS Delbert L. Johnson, Table of n, a(n) for n = 1..28 MATHEMATICA Select[Range[3, 10^7], PowerMod[2, #, #*(# - 1)*(# - 2)/6] == 2 &] (* Amiram Eldar, Sep 27 2020 *) PROG (PARI) is(n) = n>=3 && Mod(2, n*(n-1)*(n-2)/6)^n ==2 CROSSREFS Cf. A337818, A337846. Sequence in context: A222496 A086158 A158878 * A337859 A184314 A300938 Adjacent sequences: A337855 A337856 A337857 * A337859 A337860 A337861 KEYWORD nonn AUTHOR Benoit Cloitre, Sep 26 2020 EXTENSIONS a(12)-a(18) from Amiram Eldar, Sep 27 2020 a(19)-a(25) from Delbert L. Johnson, Mar 27 2024 STATUS approved

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Last modified August 11 20:46 EDT 2024. Contains 375073 sequences. (Running on oeis4.)