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A287295
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a(2n-1) is concatenation of sequence (1,3,..,2n-3,2n-1,2n-3,..3,1) and a(2n) is concatenation of sequence (1,3,..,2n-3,2n-1,2n-1,2n-3,..3,1).
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0
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1, 11, 131, 1331, 13531, 135531, 1357531, 13577531, 135797531, 1357997531, 135791197531, 13579111197531, 1357911131197531, 135791113131197531, 13579111315131197531, 1357911131515131197531, 135791113151715131197531, 13579111315171715131197531
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OFFSET
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1,2
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COMMENTS
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For n = {2, 3, 13, 16, 19, 21, 67}, a(n) is prime (when n <= 2800).
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LINKS
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MATHEMATICA
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Block[{nn = 18, s}, s = IntegerDigits@ Range[1, nn, 2]; Table[FromDigits@ Flatten@ Join[#, Reverse[If[EvenQ@ n, #, Most@ #] &@ #]] &@ Take[s, Ceiling[n/2]], {n, nn}]] (* Michael De Vlieger, May 23 2017 *)
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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STATUS
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approved
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