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 A283185 Numbers k such that (86*10^k + 121)/9 is prime. 0
 0, 1, 4, 6, 24, 52, 60, 76, 94, 106, 136, 196, 283, 319, 486, 1560, 1615, 1747, 2188, 2359, 5004, 5608, 9301, 22086, 30391, 76128, 90588 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For k>1, numbers such that the digit 9 followed by k-2 occurrences of the digit 5 followed by the digits 69 is prime (see Example section). a(28) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 95w69. EXAMPLE 4 is in this sequence because (86*10^4 + 121)/9 = 95569 is prime. Initial terms and primes associated: a(1) = 0, 23; a(2) = 1, 109; a(3) = 4, 95569; a(4) = 6, 9555569; a(5) = 24, 9555555555555555555555569; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(86*10^# + 121)/9] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A164532 A098660 A122174 * A034458 A240290 A067001 Adjacent sequences:  A283182 A283183 A283184 * A283186 A283187 A283188 KEYWORD nonn,more,hard,changed AUTHOR Robert Price, Mar 02 2017 STATUS approved

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Last modified January 18 10:53 EST 2019. Contains 319271 sequences. (Running on oeis4.)