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 A275096 Numbers n such that 2*10^n + 89 is prime. 0
 1, 3, 4, 8, 9, 10, 13, 20, 27, 74, 89, 93, 137, 139, 296, 310, 662, 749, 1249, 2540, 2848, 3309, 8677, 11573, 15286, 17125, 39526, 42187, 44476, 47823, 92897 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For n>1, numbers n such that the digit 2 followed by n-2 occurrences of the digit 0 followed by the digits 89 is prime (see Example section). a(32) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 20w89. EXAMPLE 3 is in this sequence because 2*10^3 + 89 = 2089 is prime. Initial terms and associated primes: a(1) = 1, 109; a(2) = 3, 2089; a(3) = 4, 20089; a(4) = 8, 200000089; a(5) = 9, 2000000089, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[2*10^# + 89] &] PROG (MAGMA) [n: n in [1..500] | IsPrime(2*10^n+89)]; // Vincenzo Librandi, Jul 17 2016 (PARI) is(n)=ispseudoprime(2*10^n+89) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A296497 A019811 A075746 * A109826 A228145 A243064 Adjacent sequences:  A275093 A275094 A275095 * A275097 A275098 A275099 KEYWORD nonn,more AUTHOR Robert Price, Jul 16 2016 STATUS approved

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Last modified January 26 01:48 EST 2020. Contains 331270 sequences. (Running on oeis4.)