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A275236
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Numbers n such that (28*10^n-97)/3 is prime.
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0
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1, 5, 8, 20, 27, 56, 74, 81, 107, 217, 294, 326, 525, 645, 667, 764, 863, 1885, 1961, 2913, 3056, 3192, 3327, 5480, 8455, 22797, 50147, 89141, 96265
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OFFSET
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1,2
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COMMENTS
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For n>1, numbers n such that the digit 9 followed by n-2 occurrences of the digit 3 followed by the digits 01 is prime (see Example section).
a(30) > 10^5.
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LINKS
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EXAMPLE
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5 is in this sequence because (28*10^5-97)/3 = 877 is prime.
Initial terms and primes associated:
a(1) = 1, 61;
a(2) = 5, 933301;
a(3) = 8, 933333301;
a(4) = 20, 933333333333333333301;
a(5) = 27, 9333333333333333333333333301, etc.
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MATHEMATICA
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Select[Range[0, 100], PrimeQ[(28*10^#-97)/3 && # > 0] &] (* Corrected by Georg Fischer, Jul 22 2019 *)
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PROG
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(Magma) [n: n in [1..500] | IsPrime((28*10^n-97) div 3)]; // Vincenzo Librandi, Jul 21 2016
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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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STATUS
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approved
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