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A276698
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Numbers k such that (25*10^k - 37) / 3 is prime.
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0
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1, 2, 7, 17, 24, 32, 66, 67, 74, 92, 104, 117, 188, 260, 279, 336, 348, 369, 547, 619, 860, 2735, 7932, 11874, 14867, 40153, 171849, 176715
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OFFSET
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1,2
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COMMENTS
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For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 21 is prime (see Example section).
a(29) > 2*10^5.
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LINKS
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EXAMPLE
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2 is in this sequence because (25*10^2 - 37) / 3 = 821 is prime.
Initial terms and primes associated:
a(1) = 1, 71;
a(2) = 2, 821;
a(3) = 7, 83333321;
a(4) = 17, 833333333333333321;
a(5) = 24, 8333333333333333333333321, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(25*10^# - 37) / 3] &]
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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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