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A280206
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Numbers k such that (14*10^k - 53) / 3 is prime.
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0
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1, 2, 3, 4, 5, 11, 28, 40, 65, 95, 187, 201, 202, 211, 316, 331, 559, 746, 1307, 2139, 3571, 5843, 6545, 12717, 32804, 46389, 72326, 135301
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OFFSET
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1,2
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COMMENTS
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For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 49 is prime (see Example section).
a(29) > 2*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (14*10^3 - 53) / 3 = 4649 is prime.
Initial terms and primes associated:
a(1) = 1, 29;
a(2) = 2, 449;
a(3) = 3, 4649;
a(4) = 4, 46649;
a(5) = 5, 466649; etc.
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MATHEMATICA
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Select[Range[1, 100000], PrimeQ[(14*10^# - 53) / 3] &]
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PROG
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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