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A274331
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Numbers k such that (148*10^k - 1)/3 is prime.
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0
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2, 3, 4, 5, 9, 27, 35, 44, 88, 104, 205, 290, 302, 381, 400, 686, 917, 1150, 2278, 2757, 3220, 3316, 7469, 9535, 21442, 46409, 103718, 123688, 147139
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OFFSET
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1,1
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COMMENTS
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Numbers k such that the digits 49 followed by k occurrences of the digit 3 is prime (see Example section).
a(30) > 2*10^5.
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LINKS
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Table of n, a(n) for n=1..29.
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 493w.
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EXAMPLE
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3 is in this sequence because (148*10^3-1)/3 = 233329 is prime.
Initial terms and primes associated:
a(1) = 2, 4933;
a(2) = 3, 49333;
a(3) = 4, 493333;
a(4) = 5, 4933333;
a(5) = 9, 49333333333, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(148*10^# - 1)/3] &]
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PROG
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(PARI) is(n)=ispseudoprime((148*10^n - 1)/3) \\ Charles R Greathouse IV, Jun 13 2017
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CROSSREFS
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Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A162374 A323289 A065885 * A177064 A092233 A115895
Adjacent sequences: A274328 A274329 A274330 * A274332 A274333 A274334
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KEYWORD
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nonn,more
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AUTHOR
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Robert Price, Jun 18 2016
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EXTENSIONS
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a(27)-a(29) from Robert Price, Mar 18 2020
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STATUS
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approved
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