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A046720
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Subsequence of beastly primes (A186086) that are palindromes that begin and end with 7.
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6
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OFFSET
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1,1
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COMMENTS
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Next term is 7_{0}^48_666_{0}^48_7, containing 101 digits, and is too large to include here.
The number of digits in the terms is 2*A186521(n)+3: 5, 9, 15, 17, 101, 1159, 1589, 2647, 2787, 4787, 6135, 26961 (some correspond to probable primes). - Jens Kruse Andersen, Jul 13 2014
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LINKS
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FORMULA
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MATHEMATICA
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Select[Table[(7*10^(n + 2) + 666)*10^n + 7, {n, 7}], PrimeQ] (* Arkadiusz Wesolowski, Sep 08 2011 *)
Select[Table[With[{s=PadRight[{7}, n, 0]}, FromDigits[Join[s, {6, 6, 6}, Reverse[s]]]], {n, 8}], PrimeQ] (* Harvey P. Dale, Aug 05 2024 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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