A174178 Numbers n such that 10^n+2*n+1 is prime.

0, 1, 4, 24, 43, 94, 193, 204, 379, 405, 675, 3811, 10239, 26809

Offset

1,3

Comments

a(15) > 10^5. - Robert Price, Mar 13 2015

Links

Table of n, a(n) for n=1..14.

Mathematica

Select[Range[0, 5000], PrimeQ[(10^# + 2*# + 1)] &] (* Vincenzo Librandi, Oct 05 2012 *)

Prog

(Magma) [n: n in [0..400] | IsPrime(10^n+2*n+1)];
(PARI) is(n)=ispseudoprime(10^n+2*n+1) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

Cf. A173840 (associated primes).

Sequence in context: A121024 A120622 A031117 * A139245 A224242 A066770

Adjacent sequences: A174175 A174176 A174177 * A174179 A174180 A174181

Keyword

nonn,hard,more

Author

Vincenzo Librandi, Mar 11 2010

Extensions

a(10)-a(12) from Vincenzo Librandi, Oct 05 2012

Prepended a(1)=0 and added a(13)-a(14) by Robert Price, Mar 13 2015

Status

approved