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A186521
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Numbers n>0 such that (7*10^(n+2)+666)*10^n+7 is prime.
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2
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1, 3, 6, 7, 49, 578, 793, 1322, 1392, 2392, 3066, 13479
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OFFSET
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1,2
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COMMENTS
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Or, indices of primes in A046720. Rudolf Ondrejka calls these "beastly palindromic primes".
Some of the larger entries may only correspond to probable primes.
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LINKS
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MATHEMATICA
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Select[Range[10^3], PrimeQ[(7*10^(# + 2) + 666)*10^# + 7] &] (* Arkadiusz Wesolowski, Sep 08 2011 *)
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CROSSREFS
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KEYWORD
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nonn,base,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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