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A283448
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Numbers k such that (265*10^k + 11)/3 is prime.
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0
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1, 2, 3, 5, 14, 18, 38, 65, 217, 218, 342, 560, 648, 962, 1151, 2043, 2113, 2641, 5738, 13295, 15793, 20424, 35729, 48474, 62298, 88077
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OFFSET
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1,2
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COMMENTS
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For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 3 followed by the digit 7 is prime (see Example section).
a(27) > 2*10^5.
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LINKS
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EXAMPLE
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3 is in this sequence because (265*10^3 + 11)/3 = 88337 is prime.
Initial terms and associated primes:
a(1) = 1, 887;
a(2) = 2, 8837;
a(3) = 3, 88337;
a(4) = 5, 8833337;
a(5) = 14, 8833333333333337; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(265*10^# + 11)/3] &]
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PROG
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(PARI) isok(n) = isprime((265*10^n + 11)/3); \\ Indranil Ghosh, Mar 09 2017
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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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