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A285377
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Numbers k such that (41*10^k + 373)/9 is prime.
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1
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3, 5, 6, 9, 11, 53, 105, 125, 137, 228, 789, 1259, 1661, 1697, 1785, 3737, 6054, 7614, 11819, 27366, 28320, 48678, 69321, 76067, 97085
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OFFSET
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1,1
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COMMENTS
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For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 5 followed by the digits 97 is prime (see Example section).
a(26) > 2*10^5.
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LINKS
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EXAMPLE
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5 is in this sequence because (41*10^5 + 373)/9 = 455597 is prime.
Initial terms and associated primes:
a(1) = 3, 4597;
a(2) = 5, 455597;
a(3) = 6, 4555597;
a(4) = 9, 4555555597;
a(5) = 11, 455555555597; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(41*10^# + 373)/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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STATUS
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approved
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