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 A291606 Numbers k such that 44*10^k + 3 is prime. 0
 0, 1, 6, 7, 27, 51, 67, 69, 115, 153, 346, 351, 1152, 1807, 2508, 4470, 4875, 5277, 7527, 10339, 11407, 21807, 26199, 46473, 68368 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For k>0, numbers such that the digits 44 followed by k-1 occurrences of the digit 0 followed by the digit 3 is prime (see Example section). a(28) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 440w3 EXAMPLE 1 is in this sequence because 44*10^1 + 3 = 443 is prime. Initial terms and primes associated: a(1) = 0, 47; a(2) = 1, 443; a(3) = 6, 44000003; a(4) = 7, 440000003; a(5) = 27, 44000000000000000000000000003; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[44*10^# + 3] &] PROG (PARI) isok(k) = ispseudoprime(44*10^k + 3) \\ Altug Alkan, Aug 27 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A054289 A041078 A067229 * A041535 A129214 A042419 Adjacent sequences:  A291603 A291604 A291605 * A291607 A291608 A291609 KEYWORD nonn,more,hard AUTHOR Robert Price, Aug 27 2017 STATUS approved

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Last modified February 26 02:19 EST 2020. Contains 332270 sequences. (Running on oeis4.)