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 A289051 Numbers k such that 13*10^k + 1 is prime. 1
 1, 2, 3, 7, 16, 53, 95, 105, 125, 163, 358, 423, 562, 1774, 3459, 13957, 17962, 51179, 65963, 72808 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k>0, numbers such that the digits 13 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section). a(21) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 130w1. EXAMPLE 2 is in this sequence because 13*10^3 + 1 = 1301 is prime. Initial terms and primes associated: a(1) = 1, 131; a(2) = 2, 1301; a(3) = 3, 13001; a(4) = 7, 130000001; a(5) = 16, 130000000000000001; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[13*10^# + 1] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A246829 A296231 A089125 * A282320 A002854 A036356 Adjacent sequences:  A289048 A289049 A289050 * A289052 A289053 A289054 KEYWORD nonn,more,hard AUTHOR Robert Price, Jun 22 2017 STATUS approved

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Last modified May 15 16:02 EDT 2021. Contains 343920 sequences. (Running on oeis4.)