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A271645
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Numbers k such that (23*10^k + 91)/3 is prime.
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0
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1, 2, 4, 15, 16, 19, 20, 26, 38, 47, 52, 75, 122, 191, 246, 257, 294, 305, 374, 592, 682, 729, 1092, 2053, 2997, 4065, 13936, 17214, 19059, 37433, 142105, 214633, 242909
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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 7 followed by k-2 occurrences of the digit 6 followed by the digits 97 is prime (see Example section).
a(34) > 3*10^5.
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LINKS
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EXAMPLE
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4 is in this sequence because (23*10^4 + 91)/3 = 76697 is prime.
Initial terms and primes associated:
a(1) = 1, 107;
a(2) = 2, 797;
a(3) = 4, 76697;
a(4) = 15, 7666666666666697;
a(5) = 16, 76666666666666697, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(23*10^# + 91)/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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