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%I #14 Dec 15 2017 17:36:03
%S 53,353,2160617,479,146053847,18533465459,18588601,444444443,
%T 10987654321234567891,41824630287288128897,24899126702236725259,
%U 131211109876543212345678910111213,59722151033999393,1081735780698166140181,40378532802777469135803086419727527803285379
%N a(1) = 1, a(n) = the largest prime divisor of concatenation of sequence (n,n-1,..,2,1,2,..,n-1,n) A007942.
%H M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/SmMirror.txt">Smarandache Mirror Sequence</a>.
%e a(4) is 2160617 because 4321234 = 2.'2160617'.
%t 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 *)
%Y Cf. A007942.
%K nonn,base
%O 2,1
%A _Jason Earls_, Sep 09 2002
%E Edited by _Charles R Greathouse IV_, Apr 28 2010
%E More terms from _Harvey P. Dale_, Sep 05 2015
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