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 A286431 Numbers k such that (22*10^k + 53)/3 is prime. 0
 2, 3, 4, 5, 8, 9, 16, 17, 18, 36, 54, 69, 183, 200, 240, 846, 1424, 2511, 4750, 13854, 15414, 103450, 128094, 132746 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For k>1, numbers such that the digit 7 followed by k-2 occurrences of the digit 3 followed by the digits 51 is prime (see Example section). a(25) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 73w51. EXAMPLE 3 is in this sequence because (22*10^3 + 53)/3 = 7351 is prime. Initial terms and primes associated: a(1) = 2, 751; a(2) = 3, 7351; a(3) = 4, 73351; a(4) = 5, 733351; a(5) = 8, 733333351; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(22*10^# + 53)/3] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A085152 A264886 A287117 * A015931 A330400 A306044 Adjacent sequences:  A286428 A286429 A286430 * A286432 A286433 A286434 KEYWORD nonn,more,hard AUTHOR Robert Price, May 09 2017 EXTENSIONS a(22)-a(24) from Robert Price, Jul 06 2019 STATUS approved

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Last modified August 5 01:51 EDT 2021. Contains 346456 sequences. (Running on oeis4.)