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 A282667 Numbers k such that (7*10^k + 107)/3 is prime. 0
 1, 2, 4, 8, 12, 15, 21, 31, 48, 151, 723, 879, 1811, 3444, 5104, 5512, 5695, 6723, 9082, 14944, 15184, 18512, 35141, 81985, 123563, 155203, 165134, 165239 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k>1, numbers such that the digit 2 followed by k-2 occurrences of the digit 3 followed by the digits 69 is prime (see Example section). a(29) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 23w69. EXAMPLE 4 is in this sequence because (7*10^4 + 107)/3 = 23369 is prime. Initial terms and primes associated: a(1) = 1, 59; a(2) = 2, 269; a(3) = 4, 23369; a(4) = 8, 233333369; a(5) = 12, 2333333333369; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(7*10^# + 107)/3] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A064711 A050865 A288514 * A124395 A334167 A024908 Adjacent sequences:  A282664 A282665 A282666 * A282668 A282669 A282670 KEYWORD nonn,more,hard AUTHOR Robert Price, Feb 20 2017 EXTENSIONS a(25)-a(28) from Robert Price, Feb 21 2018 STATUS approved

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Last modified December 3 02:56 EST 2020. Contains 338899 sequences. (Running on oeis4.)