

A174178


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


2



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



