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 A270890 Numbers k such that (8*10^k + 49)/3 is prime. 497
 0, 1, 2, 3, 4, 5, 6, 10, 24, 33, 34, 35, 45, 52, 56, 62, 65, 103, 166, 424, 886, 1418, 1825, 4895, 5715, 7011, 7810, 9097, 12773, 14746, 20085, 25359, 27967, 46629, 48507, 68722, 74944, 102541, 118960, 157368 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For k>2, numbers such that the digit 2 followed by k-3 occurrences of the digit 6 followed by the digits 83 is prime (see Example section). a(41) > 2*10^5. LINKS Makoto Kamada, Search for 26w83. EXAMPLE 3 is in this sequence because (8*10^3 + 49)/3 = 2683 is prime. Initial terms and primes associated: a(1) = 0, 19; a(2) = 1, 43; a(3) = 2, 283; a(4) = 3, 2683; a(5) = 4, 26683; a(6) = 5, 266683, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(8*10^# + 49)/3] &] PROG (PARI) is(n)=isprime((8*10^n + 49)/3) \\ Charles R Greathouse IV, Feb 16 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831. Sequence in context: A271341 A306109 A281513 * A010350 A306581 A269858 Adjacent sequences:  A270887 A270888 A270889 * A270891 A270892 A270893 KEYWORD nonn,more AUTHOR Robert Price, Mar 25 2016 EXTENSIONS a(38)-a(40) from Robert Price, May 23 2020 STATUS approved

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Last modified January 17 06:58 EST 2021. Contains 340214 sequences. (Running on oeis4.)