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A070274
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Numbers n such that sum of digits of n equals the squarefree part of n.
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7
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1, 2, 3, 5, 6, 7, 12, 24, 100, 150, 200, 300, 320, 375, 500, 600, 640, 700, 704, 735, 832, 960, 1014, 1088, 1200, 1815, 2023, 2400, 2535, 2940, 3549, 3610, 3840, 4046, 4335, 4913, 5054, 5376, 5415, 5491, 6069, 6137, 6358, 6647, 7260, 7581, 7942, 8959, 9386
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OFFSET
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1,2
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COMMENTS
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The squarefree part of x, core(x), is the smallest integer such that x*core(x) is a square.
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LINKS
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MATHEMATICA
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core[n_]:=Block[{f=FactorInteger[n], p, e}, {p, e} = Transpose[f]; Times@@ (p^Mod[e, 2])]; Select[Range[10^4], core[#] == Plus @@ IntegerDigits[#] &] (* Giovanni Resta, Apr 21 2017 *)
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PROG
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(PARI) list(lim)=my(v=List()); forfactored(n=1, lim\1, if(core(n)==sumdigits(n[1]), listput(v, n[1]))); Vec(v) \\ Charles R Greathouse IV, Nov 05 2017
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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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EXTENSIONS
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STATUS
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approved
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