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A270448 Numbers n such that 10^n-8001 is prime. 0
4, 6, 8, 11, 12, 14, 23, 26, 42, 50, 54, 55, 66, 136, 145, 151, 200, 214, 888, 896, 1674, 2311, 2799, 2836, 2912, 5192, 5907, 8644, 8681, 11914, 18140, 27383, 36549, 57358, 84582, 161253, 167639, 186842, 193230 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For n>3, numbers such that n-4 occurrences of the digit 9 followed by the digits 1999 is prime (see Example section).

a(40) > 2*10^5.

LINKS

Table of n, a(n) for n=1..39.

Makoto Kamada, Search for 9w1999.

EXAMPLE

4 is in this sequence because 10^4-8001 = 1999 is prime.

Initial terms and primes associated:

a(1) = 4, 1999;

a(2) = 6, 991999;

a(3) = 8, 99991999;

a(4) = 11, 99999991999;

a(5) = 12, 999999991999, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[10^4-8001] &]

PROG

(PARI) isok(n) = isprime(10^n-8001); \\ Michel Marcus, Mar 18 2016

(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(10^n-8001), print1(n, ", "))); \\ Altug Alkan, Mar 18 2016

CROSSREFS

Cf. A056654, A268448, A269303, A270339.

Sequence in context: A295287 A079254 A091178 * A152019 A091181 A189462

Adjacent sequences:  A270445 A270446 A270447 * A270449 A270450 A270451

KEYWORD

nonn,more

AUTHOR

Robert Price, Mar 17 2016

EXTENSIONS

a(36)-a(39) from Robert Price, Mar 27 2018

STATUS

approved

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Last modified May 22 21:17 EDT 2019. Contains 323504 sequences. (Running on oeis4.)