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 A271618 Numbers k such that 10^k-801 is prime. 0
 3, 4, 6, 14, 15, 16, 20, 46, 52, 114, 165, 468, 504, 568, 713, 748, 899, 958, 992, 1043, 1348, 2388, 3182, 4102, 8847, 10899, 11908, 18852, 25214, 40151, 40290, 51207, 71910, 166324 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n>2, numbers such that n-3 occurrences of the digit 9 followed by the digits 199 is prime (see Example section). a(35) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 9w199. EXAMPLE 6 is in this sequence because 10^6-801 = 999199 is prime. Initial terms and primes associated: a(1) = 3, 199; a(2) = 4, 9199; a(3) = 6, 999199; a(4) = 14, 99999999999199; a(5) = 15, 999999999999199, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[10^#-801] &] PROG (PARI) is(n)=ispseudoprime(10^n-801) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A143100 A327584 A180859 * A137820 A049892 A063477 Adjacent sequences:  A271615 A271616 A271617 * A271619 A271620 A271621 KEYWORD nonn,more AUTHOR Robert Price, Apr 11 2016 EXTENSIONS a(34) from Robert Price, Feb 14 2018 STATUS approved

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Last modified June 14 05:51 EDT 2021. Contains 345018 sequences. (Running on oeis4.)