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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 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.)