OFFSET
1,2
COMMENTS
17 divides a(n) for n > 1.
MATHEMATICA
Select[Range[350000], Mod[PowerMod[18, #^2, #^3] - 1, #^3] == 0 &] (* Julien Kluge, Sep 20 2016 *)
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, May 14 2010
EXTENSIONS
Three more terms from Max Alekseyev, Oct 02 2010
STATUS
approved