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A137318
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Concatenation of segments of the digit sequence 1 3 1 3 1 3 1 3 1 3 1 3 1 3 1 3 1 3....
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1
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1, 31, 313, 1313, 13131, 313131, 3131313, 13131313, 131313131, 3131313131, 31313131313, 131313131313, 1313131313131, 31313131313131, 313131313131313, 1313131313131313, 13131313131313131, 313131313131313131
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OFFSET
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1,2
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COMMENTS
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A000042 is 1,11,111,1111,11111,... concatenation of 111111111111111....
A002276 is 2,22,222,2222,22222,... concatenation of 222222222222222....
A133013 is 2,35,71113,... concatenation of 2 3 5 7 11 13 17 19 23 29,...
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LINKS
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FORMULA
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O.g.f.: x*(100x^4 + 200x^3 + 83x^2 + 20x + 1)/((10x-1)(100x^2+1)(x-1)(x^2+1)). - R. J. Mathar, Apr 09 2008
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MATHEMATICA
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Module[{nn=20}, FromDigits/@TakeList[PadRight[{}, (nn(nn+1))/2, {1, 3}], Range[ nn]]] (* Harvey P. Dale, Aug 04 2021 *)
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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