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 A271640 Numbers k such that 3*10^k + 73 is prime. 0
 1, 2, 5, 6, 13, 37, 50, 55, 71, 89, 217, 352, 355, 398, 449, 668, 742, 870, 1360, 1579, 2848, 3774, 5039, 5051, 6134, 6824, 7255, 12586, 17106, 27502, 30581, 33817, 97399, 170800, 172219, 177872 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k > 1, numbers such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 73 is prime (see Example section). a(37) > 2*10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 30w73. EXAMPLE 5 is in this sequence because 3*10^5 + 73 = 300073 is prime. Initial terms and primes associated: a(1) = 1, 103; a(2) = 2, 373; a(3) = 5, 300073; a(4) = 6, 3000073; a(5) = 13, 30000000000073, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[3*10^# + 73] &] PROG (PARI) is(n)=ispseudoprime(3*10^n + 73) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A243799 A029544 A058668 * A180744 A092790 A105043 Adjacent sequences:  A271637 A271638 A271639 * A271641 A271642 A271643 KEYWORD nonn,more AUTHOR Robert Price, Apr 11 2016 EXTENSIONS a(34)-a(36) from Robert Price, Aug 10 2018 STATUS approved

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Last modified April 22 04:04 EDT 2019. Contains 322329 sequences. (Running on oeis4.)