OFFSET
1,2
COMMENTS
Numbers n such that '108347' (prime) appended to n times the digit 2 is prime.
a(n) mod 3 <= 1.
EXAMPLE
1 appears because 2108347 ('2' prepended to '108347') is prime.
MATHEMATICA
Select[ Range[2000], PrimeQ[(2^(#+7) * 5^(#+6) - 1024877) / 9] &] (*Or*)
Select[ Range[2000], PrimeQ[5*(2^(#+7) * 5^(#+5) - 204979) / 9 + 2] &]
PROG
(Magma) [n: n in [1..700] |IsPrime((2^(n+7)*5^(n+6)-1024877) div 9)]; // Vincenzo Librandi, Jan 13 2016
(PARI) is(n) = ispseudoprime((2^(n+7)*5^(n+6) - 1024877) / 9); \\ Altug Alkan, Jan 15 2016
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Mikk Heidemaa, Jan 07 2016
STATUS
approved