%I #29 Jul 19 2021 15:04:35
%S 5,7,179,229,439,557,6113,223999,327001,2264611
%N Numbers n such that (11^n + 1)/12 is a prime.
%H Paul Bourdelais, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=NMBRTHRY;417ab0d6.0906">A Generalized Repunit Conjecture</a>
%H J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H H. Dubner and T. Granlund, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/DUBNER/dubner.html">Primes of the Form (b^n+1)/(b+1)</a>, J. Integer Sequences, 3 (2000), #P00.2.7.
%H H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repunit.html">Repunit</a>
%t lst={};Do[p=(11^n+1)/12;If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Sep 29 2008 *)
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Sep 15 2000
%E a(8) corresponds to a probable prime discovered by _Paul Bourdelais_, Feb 12 2010
%E a(9) corresponds to a probable prime discovered by _Paul Bourdelais_, Sep 30 2013
%E a(10) by _Paul Bourdelais_, Jul 19 2021