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
a(18) = 28311553. - Chai Wah Wu, May 18 2020
a(16) = 4457323664018586376077313, a(20) = 46179488366593. - Max Alekseyev, Aug 29 2023
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
KEYWORD
hard,more,nonn
AUTHOR
Arkadiusz Wesolowski, Nov 04 2011
STATUS
approved