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A076786
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Squarefree numbers such that in decimal representation all their prefixes are also squarefree.
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1
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1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 51, 53, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 101, 102, 103, 105, 106, 107, 109, 110, 111, 113, 114, 115, 118, 119, 130, 131, 133, 134, 137
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OFFSET
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1,2
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COMMENTS
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a(n)=A005117(n) for n<=26, but A005117(27)=41 is not a term, as 4=2^2 is not squarefree.
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LINKS
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EXAMPLE
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143=11*13 is a term, as also 14=2*7 and 1 are squarefree.
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MATHEMATICA
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Select[Range[200], AllTrue[FromDigits/@Table[Take[IntegerDigits[#], {1, n}], {n, IntegerLength[#]}], SquareFreeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 23 2020 *)
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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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STATUS
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approved
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