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 A055685 Numbers k such that 2^k == -1 (mod k-1). 14
 2, 6, 66, 378, 1190, 1470, 25806, 58590, 134946, 137346, 170586, 272610, 285390, 420210, 538734, 592410, 618450, 680706, 778806, 1163066, 1520442, 1700946, 2099202, 2831010, 4020030, 4174170, 4516110, 5059890, 5215770 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The sequence is infinite. In fact, even its intersection with A006517 (given by A219037) is infinite. LINKS Chai Wah Wu, Table of n, a(n) for n = 1..1192 Kin Y. Li et al., Solution to Problem 323, Mathematical Excalibur 14(2), 2009, p. 3. FORMULA a(n) = A296369(n) + 1. MATHEMATICA Do[If[PowerMod[2, n, n-1]==n-2, Print[n]], {n, 2, 12900000}] PROG (Python) A055685_list = [n for n in range(2, 10**6) if pow(2, n, n-1) == n-2] # Chai Wah Wu, Nov 04 2019 CROSSREFS Cf. A064935, A006517, A219037, A296369. Sequence in context: A061999 A066756 A070872 * A368511 A368512 A262047 Adjacent sequences: A055682 A055683 A055684 * A055686 A055687 A055688 KEYWORD nonn AUTHOR Robert G. Wilson v, Jun 09 2000 EXTENSIONS Edited by Max Alekseyev, Oct 11 2012 Incorrect term 4285390 removed by Chai Wah Wu, Nov 04 2019 STATUS approved

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Last modified September 12 11:52 EDT 2024. Contains 375851 sequences. (Running on oeis4.)