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 A273042 Numbers k such that (28*10^k + 191)/3 is prime. 0
 0, 1, 2, 3, 5, 6, 9, 10, 33, 49, 92, 109, 548, 757, 814, 1289, 1460, 1644, 2782, 6355, 8028, 9276, 9366, 9765, 12002, 12089, 14491, 16180, 29102, 30989, 151682, 183403, 190105 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For k>1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 3 followed by the digits 97 is prime (see Example section). a(34) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 93w97. EXAMPLE 3 is in this sequence because (28*10^3 + 191)/3 = 9397 is prime. Initial terms and primes associated: a(1) = 0, 73; a(2) = 1, 157: a(3) = 2, 997; a(4) = 3, 9397; a(5) = 5, 933397, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(28*10^# + 191)/3] &] PROG (PARI) is(n)=ispseudoprime((28*10^n + 191)/3) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A018278 A137809 A219035 * A014838 A026459 A026461 Adjacent sequences:  A273039 A273040 A273041 * A273043 A273044 A273045 KEYWORD nonn,more AUTHOR Robert Price, May 13 2016 EXTENSIONS a(31)-a(33) from Robert Price, Feb 27 2020 STATUS approved

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Last modified August 1 03:52 EDT 2021. Contains 346384 sequences. (Running on oeis4.)