OFFSET
1,3
COMMENTS
If 6^n is of the form T(x,y) = 2xy+x+y [A083487] then 2*6^n+1 is not prime. - Vincenzo Librandi, Nov 13 2010
a(1)-a(37) proven prime by the primality proving program LLR. - Robert Price, Jan 08 2016
a(38) > 2.5*10^5. - Robert Price, Jan 08 2016
MATHEMATICA
Select[Range[0, 2000], PrimeQ[2*6^# + 1] &] (* Vladimir Joseph Stephan Orlovsky, Jan 31 2012 *)
PROG
(PARI) isok(n) = isprime(2*6^n+1); \\ Michel Marcus, Jan 08 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Jun 04 2006
EXTENSIONS
More terms from Pierre CAMI, Jun 16 2006
a(32)-a(37) from Robert Price, Jan 08 2016
STATUS
approved