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 A284886 Numbers k such that (14*10^k-101)/3 is prime. 0
 1, 2, 4, 6, 14, 20, 305, 470, 507, 1104, 1152, 1725, 1944, 5864, 6785, 7446, 11460, 12412, 16302, 19787, 24029, 27240, 67235, 83471, 89480, 116112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 33 is prime (see Example section). a(27) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 46w33. EXAMPLE 4 is in this sequence because (14*10^4 - 101)/3 = 46633 is prime. Initial terms and primes associated: a(1) = 1, 13; a(2) = 2, 433; a(3) = 4, 46633; a(4) = 6, 4666633; a(5) = 14, 466666666666633; etc. MATHEMATICA Select[Range[1, 100000], PrimeQ[(14*10^# - 101)/3] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A062112 A226302 A337499 * A249339 A332754 A307676 Adjacent sequences:  A284883 A284884 A284885 * A284887 A284888 A284889 KEYWORD nonn,more,hard AUTHOR Robert Price, Apr 04 2017 EXTENSIONS a(26) from Robert Price, Feb 23 2019 STATUS approved

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Last modified January 27 16:41 EST 2022. Contains 350611 sequences. (Running on oeis4.)