OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..100
MATHEMATICA
Select[Prime[Range[85000]], PowerMod[3, #-1, #(#-2)]==1&]//Quiet (* Harvey P. Dale, Mar 19 2019 *)
PROG
(PARI) lista(nn) = {forprime(p=3, nn, if (! ((3^(p-1)-1) % (p*(p-2))), print1(p, ", ")); ); }
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 09 2003
EXTENSIONS
More terms from Michel Marcus, Dec 02 2013
STATUS
approved