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A282620
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Numbers k such that (67*10^k + 17)/3 is prime.
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0
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1, 2, 4, 8, 11, 20, 21, 32, 33, 41, 93, 187, 265, 380, 1088, 1459, 1671, 7328, 11524, 14167, 21719, 47439, 74045
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OFFSET
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1,2
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COMMENTS
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For k > 1, numbers k such that the digits 22 followed by k-1 occurrences of the digit 3 followed by the digit 9 is prime (see Example section).
a(24) > 2*10^5.
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LINKS
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EXAMPLE
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4 is in this sequence because (67*10^4 + 17)/3 = 223339 is prime.
Initial terms and associated primes:
a(1) = 1, 229;
a(2) = 2, 2239;
a(3) = 4, 223339;
a(4) = 8, 2233333339;
a(5) = 11, 2233333333339; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(67*10^# + 17)/3] &]
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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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STATUS
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approved
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