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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 17 21:36 EDT 2019. Contains 325109 sequences. (Running on oeis4.)