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A136996
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Numbers k such that k and k^2 use only the digits 1, 2, 4 and 7.
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0
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OFFSET
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1,2
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COMMENTS
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Generated with DrScheme.
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LINKS
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EXAMPLE
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2777177421^2 = 7712714427712211241.
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MATHEMATICA
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Module[{c = {1, 2, 4, 7}}, Select[Flatten[Table[FromDigits /@ Tuples[c, n], {n, 10}]], SubsetQ[c, IntegerDigits[#^2]] &]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 02 2017 *)
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CROSSREFS
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KEYWORD
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base,nonn,more
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AUTHOR
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Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
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STATUS
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approved
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