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A225743
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Triangular array: row n is least squarefree word of length n using positive integers.
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1
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1, 1, 2, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 3, 1, 1, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1, 4, 1, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 4
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OFFSET
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1,3
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COMMENTS
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Squarefree means that the word contains no consecutive identical subwords.
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LINKS
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EXAMPLE
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The first 10 rows are shown here:
1
1 2
1 2 1
1 2 1 3
1 2 1 3 1
1 2 1 3 1 2
1 2 1 3 1 2 1
1 2 1 3 1 2 1 4
1 2 1 3 1 2 1 4 1
1 2 1 3 1 2 1 4 1 2
1 contains no square; 11 contains a square but 12 does not; 121 contains no square; both 1211 and 1212 have squares but 1213 does not.
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MATHEMATICA
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squareFreeQ[string_] := StringFreeQ[string, a__ ~~ a__]; t = {}; s = Table[AppendTo[t, NestWhile[# + 1 &, 1, ! squareFreeQ[ToString[FromDigits[Append[t, #]]]] &]], {20}];
Map[IntegerExponent[2*#, 2] &, Range[Range[33]]] (* A225743 array, by formula *)
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CROSSREFS
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Cf. A001511 (the limiting sequence)
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KEYWORD
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AUTHOR
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STATUS
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approved
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