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A294227
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Numbers k such that (16*10^k + 167)/3 is prime.
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0
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0, 1, 5, 8, 12, 13, 14, 15, 33, 98, 123, 260, 485, 1340, 1674, 1775, 5988, 7039, 9421, 15149, 21751, 30882, 36517, 85839, 121633, 131180, 140091, 188823
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OFFSET
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1,3
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COMMENTS
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For k>1, numbers such that the digit 5 followed by k-2 occurrences of the digit 3 followed by the digits 89 is prime (see Example section).
a(29) > 2*10^5.
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LINKS
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EXAMPLE
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5 is in this sequence because (16*10^5 + 167)/3 = 533389 is prime.
Initial terms and primes associated:
a(1) = 0, 61;
a(2) = 1, 109;
a(3) = 5, 533389;
a(4) = 8, 533333389;
a(5) = 12, 5333333333389; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(16*10^# + 167)/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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