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

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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..7.

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A110066.

Sequence in context: A348590 A120306 A197425 * A193698 A188800 A297393

Adjacent sequences: A089376 A089377 A089378 * A089380 A089381 A089382

Keyword

nonn

Author

Shyam Sunder Gupta, Dec 27 2003

Extensions

One more term from Farideh Firoozbakht, Jun 11 2006

a(7) from Robert Price, Feb 14 2015

Status

approved