

A265383


Numbers k such that 10^k * (10^k  1)  1 is prime.


1



1, 6, 9, 154, 253, 1114, 1390, 2618, 5611, 12871, 15286, 108609, 132574, 164369, 188484
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OFFSET

1,2


COMMENTS

The primes arising from this construction (e.g., 999998999999) are among the primes counted in A266148. In particular, it follows that A266148(a(n)) > 0.  David A. Corneth, May 19 2016


LINKS



EXAMPLE

6 is in the sequence because 10^12  10^6  1 = 999998999999 is prime.


MATHEMATICA

Select[Range[15000], PrimeQ[10^# (10^#  1)  1] &] (* Vincenzo Librandi, Dec 08 2015 *)


PROG

(PARI) for(n=1, 9999, if(ispseudoprime(10^n*(10^n1)1), print1(n", ")))
(Magma) [n: n in [0..200]  IsPrime(10^n*(10^n1)1)]; // Vincenzo Librandi, Dec 08 2015


CROSSREFS

Cf. similar sequences listed in A265481.
A098845: Similar sequence in base 2.
A183187: Numbers k such that 10^(2k+1)10^k1 is prime, palindromic.
A266148: Number of ndigit primes in which n1 of the digits are 9's.


KEYWORD

nonn,more


AUTHOR



EXTENSIONS

a(11) from Kazuyoshi Asao, Feb 11 2002


STATUS

approved



