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A294636
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Numbers k such that 9*10^k + 23 is prime.
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0
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1, 4, 10, 16, 22, 28, 49, 66, 67, 73, 89, 136, 198, 718, 2674, 3497, 7894, 9018, 12058, 16368, 91693
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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 9 followed by k-2 occurrences of the digit 0 followed by the digits 23 is prime (see Example section).
a(22) > 2*10^5.
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LINKS
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EXAMPLE
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4 is in this sequence because 9*10^4 + 23 = 90023 is prime.
Initial terms and primes associated:
a(1) = 1, 113;
a(2) = 4, 90023;
a(3) = 10, 90000000023;
a(4) = 16, 90000000000000023;
a(5) = 22, 90000000000000000000023; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[9*10^# + 23] &]
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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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