A089379 Numbers k such that 10^k + k is prime.

1, 9, 69, 313, 451, 13807, 23769

Offset: 1

Author

Shyam Sunder Gupta, Dec 27 2003

Keywords

• nonn

Comments

a(8) > 10^5. - Robert Price, Feb 14 2015

Examples

			a(2)=9 because 10^9 + 9 is prime.
		

Crossrefs

Cf. A110066.

Programs

Mathematica

Do[If[Mod[n,3]!=2&& PrimeQ[10^n+n],Print[n]],{n,1,15500,2}] (* Farideh Firoozbakht, Jun 11 2006 *)

PARI

is(n)=ispseudoprime(10^n+n) \\ Charles R Greathouse IV, Jun 12 2017

Extensions

One more term from Farideh Firoozbakht, Jun 11 2006

a(7) from Robert Price, Feb 14 2015