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A294123
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Numbers k such that 4*10^k - 83 is prime.
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0
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2, 3, 6, 12, 24, 31, 33, 45, 66, 109, 150, 187, 345, 1000, 1026, 1189, 1959, 2754, 3405, 5047, 16291, 29958, 41547, 41709, 48908, 72274, 100257, 103981
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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 3 followed by k-2 occurrences of the digit 9 followed by the digits 17 is prime (see Example section).
a(29) > 2*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because 4*10^3 - 83 = 3917 is prime.
Initial terms and primes associated:
a(1) = 2, 317;
a(2) = 3, 3917;
a(3) = 6, 3999917;
a(4) = 12, 3999999999917;
a(5) = 24, 3999999999999999999999917; etc.
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MATHEMATICA
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Select[Range[2, 100000], PrimeQ[4*10^# - 83] &]
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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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