OFFSET
1,2
COMMENTS
No other terms below 10^15. - Max Alekseyev, Nov 26 2017
Some larger terms: 84058689739550643018360088224267, 11083544368708558891212925543084197628431243723. - Max Alekseyev, Jun 26 2011
MATHEMATICA
Join[{1, 3}, Select[Range[1, 5000], Mod[13^#, #] == 4 &]] (* G. C. Greubel, Nov 19 2017 *)
Join[{1, 3}, Select[Range[2000000], PowerMod[13, #, #] == 4 &]] (* Robert Price, Apr 10 2020 *)
PROG
(PARI) isok(n) = Mod(13, n)^n == 4; \\ Michel Marcus, Nov 19 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Zak Seidov, Feb 19 2006
EXTENSIONS
More terms from Ryan Propper, Jan 09 2008
Terms 1,3 prepended and a(12)-a(15) added by Max Alekseyev, Jun 26 2011, Nov 26 2017
STATUS
approved