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A271147
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Numbers k such that (28*10^k + 113)/3 is prime.
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0
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0, 1, 2, 3, 4, 6, 9, 12, 16, 22, 23, 42, 52, 57, 63, 117, 119, 208, 266, 324, 481, 779, 1244, 1289, 2998, 5522, 5599, 5771, 6820, 12367, 14737, 22612, 30623, 31596, 58956, 59133, 138240, 163709, 250655, 259897
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OFFSET
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1,3
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COMMENTS
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For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 3 followed by the digits 71 is prime (see Example section).
a(41) > 3*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (28*10^3+113)/3 = 9371 is prime.
Initial terms and associated primes:
a(1) = 0, 47;
a(2) = 1, 131;
a(3) = 2, 971;
a(4) = 3, 9371;
a(5) = 4, 93371;
a(6) = 6, 9333371, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(28*10^# + 113)/3] &]
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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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