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A265383
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Numbers n such that 10^n * (10^n - 1) - 1 is prime.
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1
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1, 6, 9, 154, 253, 1114, 1390, 2618, 5611, 12871, 15286, 108609, 132574, 164369, 188484
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OFFSET
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1,2
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COMMENTS
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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
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LINKS
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EXAMPLE
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6 is in the sequence because 10^12 - 10^6 - 1 = 999998999999 is prime.
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MATHEMATICA
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Select[Range[15000], PrimeQ[10^# (10^# - 1) - 1] &] (* Vincenzo Librandi, Dec 08 2015 *)
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PROG
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(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
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CROSSREFS
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Cf. similar sequences listed in A265481.
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.
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(11) from Kazuyoshi Asao, Feb 11 2002
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STATUS
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approved
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