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 A199295 Smallest prime factor of n^(n^n) + 1. 0
 2, 17, 2, 2424833, 2, 769, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Other known values: a(10)=307201, a(12)=10871635969, a(14)=977502209. - Arkadiusz Wesolowski, Jan 29 2012 a(8) > 10^20. - Max Alekseyev, Jul 31 2015 a(8) < 2^(2^24)+1 since 8^(8^8)+1 = (2^(2^24)+1) * (2^(2^25)-2^(2^24)+1) and 2^(2^24)+1 (the 24th Fermat number) is known to be composite. - Sean A. Irvine, Jun 27 2017 LINKS G. L. Honaker, Jr. and Chris Caldwell, Prime Curios! 2424833 FORMULA a(2*n-1) = 2. MATHEMATICA lst = {}; r = 7; Do[k = 1; While[True, p = k*2^(n + 1) + 1; If[PrimeQ[p] && PowerMod[n, n^n, p] + 1 == p, Break[]]; k++]; AppendTo[lst, p], {n, 2, r, 2}]; lst = Flatten[Transpose@{Table[2, {Floor[r/2]}], lst}]; If[OddQ[r], AppendTo[lst, 2], lst] (* Arkadiusz Wesolowski, Jan 29 2012 *) CROSSREFS Sequence in context: A275588 A114560 A108883 * A162623 A165234 A155895 Adjacent sequences:  A199292 A199293 A199294 * A199296 A199297 A199298 KEYWORD hard,more,nonn AUTHOR Arkadiusz Wesolowski, Nov 04 2011 STATUS approved

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Last modified February 24 17:29 EST 2020. Contains 332209 sequences. (Running on oeis4.)