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A276546
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Numbers k such that (151*10^k - 1)/3 is prime.
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0
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1, 3, 6, 15, 19, 34, 37, 88, 141, 216, 239, 246, 288, 365, 429, 762, 1879, 2309, 9555, 19843, 28348, 45058, 62879, 86963, 90669, 148020, 148601, 199003, 289877
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OFFSET
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1,2
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COMMENTS
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Numbers such that the digits 50 followed by k occurrences of the digit 3 is prime (see Example section).
a(30) > 3*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (151*10^3 - 1)/3 = 50333 is prime.
Initial terms and primes associated:
a(1) = 1, 503;
a(2) = 3, 50333;
a(3) = 6, 50333333;
a(4) = 15, 50333333333333333;
a(5) = 19, 503333333333333333333; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(151*10^# - 1)/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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EXTENSIONS
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STATUS
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approved
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