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A289051
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Numbers k such that 13*10^k + 1 is prime.
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1
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1, 2, 3, 7, 16, 53, 95, 105, 125, 163, 358, 423, 562, 1774, 3459, 13957, 17962, 51179, 65963, 72808
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OFFSET
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1,2
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COMMENTS
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For k>0, numbers such that the digits 13 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section).
a(21) > 10^5.
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LINKS
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EXAMPLE
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2 is in this sequence because 13*10^3 + 1 = 1301 is prime.
Initial terms and primes associated:
a(1) = 1, 131;
a(2) = 2, 1301;
a(3) = 3, 13001;
a(4) = 7, 130000001;
a(5) = 16, 130000000000000001; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[13*10^# + 1] &]
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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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