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A282351
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Numbers k such that (13*10^k + 437)/9 is prime.
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0
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2, 3, 6, 14, 17, 29, 41, 44, 87, 213, 354, 840, 972, 1263, 2018, 2534, 4868, 7992, 13676, 18354, 19304, 40515, 126638, 135279
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OFFSET
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1,1
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COMMENTS
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For k>1, numbers such that the digit 1 followed by k-2 occurrences of the digit 4 followed by the digits 93 is prime (see Example section).
a(25) > 2*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (13*10^3 + 437)/9 = 1493 is prime.
Initial terms and primes associated:
a(1) = 2, 193;
a(2) = 3, 1493;
a(3) = 6, 1444493;
a(4) = 14, 144444444444493;
a(5) = 17, 144444444444444493; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(13*10^# + 437)/9] &]
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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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