login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=1..7.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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