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A074836
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a(1) = 1, a(n) = the largest prime divisor of concatenation of sequence (n,n-1,..,2,1,2,..,n-1,n) A007942.
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0
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53, 353, 2160617, 479, 146053847, 18533465459, 18588601, 444444443, 10987654321234567891, 41824630287288128897, 24899126702236725259, 131211109876543212345678910111213, 59722151033999393, 1081735780698166140181, 40378532802777469135803086419727527803285379
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OFFSET
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2,1
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LINKS
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EXAMPLE
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a(4) is 2160617 because 4321234 = 2.'2160617'.
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MATHEMATICA
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Table[FactorInteger[FromDigits[Join[Flatten[IntegerDigits/@ Range[ n, 1, -1]], Flatten[IntegerDigits/@Range[2, n]]]]][[-1, 1]], {n, 2, 15}] (* Harvey P. Dale, Sep 05 2015 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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