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 A272537 Numbers n such that (28*10^n+173)/3 is prime. 0
 0, 1, 2, 3, 9, 11, 13, 15, 17, 24, 37, 44, 48, 58, 65, 104, 393, 413, 1265, 2292, 2620, 3037, 3628, 5159, 5629, 12809, 18572, 26875, 29695, 32267, 34277, 43621 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For n>1, numbers n such that the digit 9 followed by n-2 occurrences of the digit 3 followed by the digits 91 is prime (see Example section). a(33) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 93w91. EXAMPLE 3 is in this sequence because (28*10^3+173)/3 = 9391 is prime. Initial terms and primes associated: a(1) = 0, 67; a(2) = 1, 151; a(3) = 2, 991; a(4) = 3, 9391; a(5) = 9, 9333333391, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(28*10^#+173)/3] &] PROG (PARI) is(n)=ispseudoprime((28*10^n+173)/3) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A229492 A103039 A140222 * A121557 A138984 A110772 Adjacent sequences:  A272534 A272535 A272536 * A272538 A272539 A272540 KEYWORD nonn,more AUTHOR Robert Price, May 02 2016 STATUS approved

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Last modified January 17 10:30 EST 2019. Contains 319218 sequences. (Running on oeis4.)