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 A128172 Least k such that n^k mod k = n + 1. 19
 4700063497, 41459, 6821, 15853, 121129, 535, 36196439, 3827, 15084115509707, 8153, 20395, 5805311, 93929, 3736136819, 1343851, 7099195, 319, 559, 96641237093, 5053, 1535, 280517, 148731221, 869, 2062919, 17473, 803, 39259 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS a(n)=k must be odd since n and n+1 are of opposite parity. The only way this can occur is if k is odd. - Robert G. Wilson v, Aug 12 2009 [Comment corrected by Fausto A. C. Cariboni, Nov 20 2016.] LINKS Max Alekseyev, Table of n, a(n) for n = 2..43 Fausto A. C. Cariboni, Table of n, a(n) for n = 2..10000 with -1 for large entries where a(n) has not yet been found, Dec 24 2016 [With 1772 new terms, this supersedes the earlier table from Robert G. Wilson v et al.] Robert G. Wilson v et al., Table of n, a(n) for n = 2..10000 with -1 for large entries where a(n) has not yet been found EXAMPLE a(2) = A036236(3) = 4700063497. MATHEMATICA t = Table[0, {10000}]; f[n_] := Block[{k = 1}, While[k < 2097153 && PowerMod[n, k, k] != n + 1, If[ Mod[k, 6] == 1, k += 4, k += 2]]; k]; Do[ If[ t[[n]] == 0, a = f@n; If[a < 2097153, t[[n]] = a; Print[{n, a}]]], {n, 10000}]; t (* Robert G. Wilson v, Aug 12 2009 *) CROSSREFS Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127817, A127818, A127819, A127820, A127821, A128154, A128155, A128156, A128157, A128158, A128159, A128160. Cf. A128149 = Least k such that n^k mod k = n - 1. Sequence in context: A172797 A199631 A124977 * A050259 A249972 A233494 Adjacent sequences:  A128169 A128170 A128171 * A128173 A128174 A128175 KEYWORD nonn AUTHOR Alexander Adamchuk, Feb 17 2007 EXTENSIONS a(15) = A128155(16) = 3736136819 and a(16) = A128156(17) = 1343851 found by Ryan Propper, Feb 27-28 2007 a(10), a(17), a(20), a(23)-a(24), a(26), a(30)-a(31), a(33)-a(35) determined by Tyler Cadigan (tylercadigan(AT)gmail.com), Feb 21 2009 Terms corrected by Hagen von Eitzen and R. J. Mathar, Aug 05 2009 Obsolete link to a-file duplicate removed by R. J. Mathar, Aug 24 2009 Edited and a(36), a(38), a(41), a(48), a(49) added by Max Alekseyev, Feb 04, Mar 25, May 07 2012 STATUS approved

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Last modified May 25 11:46 EDT 2019. Contains 323550 sequences. (Running on oeis4.)