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A265383 Numbers n such that 10^n * (10^n - 1) - 1 is prime. 2
1, 6, 9, 154, 253, 1114, 1390, 2618, 5611, 12871, 15286, 108609, 132574, 164369 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

a(15) > 164654. - Ben Meekins, Dec 17 2016

LINKS

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

Brady Haran and Simon Pampena, Glitch Primes and Cyclops Numbers - Numberphile (2015)

M. Kamada, Near-repdigit-related prime numbers

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^n-1)-1), print1(n", ")))

(MAGMA) [n: n in [0..200] | IsPrime(10^n*(10^n-1)-1)]; // Vincenzo Librandi, Dec 08 2015

CROSSREFS

A098845: Similar sequence in base 2.

A183187: Numbers n such that 10^(2n+1)-10^n-1 is prime, palindromic.

A266148: Number of n digit primes in which n-1 of the digits are 9's.

Sequence in context: A156180 A191011 A053490 * A264375 A061110 A110460

Adjacent sequences:  A265380 A265381 A265382 * A265384 A265385 A265386

KEYWORD

nonn,more

AUTHOR

Serge Batalov, Dec 07 2015

EXTENSIONS

a(11) from Kazuyoshi Asao, Feb 11 2002

a(12) from Serge Batalov, Dec 25 2015

a(13) from Ben Meekins, Feb 16 2016

a(14) from Ben Meekins, Dec 17 2016

STATUS

approved

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Last modified September 26 06:54 EDT 2017. Contains 292502 sequences.