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A080399
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Largest squarefree number dividing sum of squares of divisors of n.
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0
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1, 5, 10, 21, 26, 10, 10, 85, 91, 130, 122, 210, 170, 10, 130, 341, 290, 455, 362, 546, 10, 610, 530, 170, 651, 170, 410, 210, 842, 130, 962, 1365, 610, 290, 130, 273, 1370, 1810, 170, 2210, 58, 10, 370, 2562, 182, 530, 2210, 3410, 2451, 3255, 290, 3570, 2810, 410
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n)=A007947[A001157(n)]
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EXAMPLE
| n=12:sigma2[12]=1+4+9+16+36+144=210, sqf-kernel=210=a(12)
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MATHEMATICA
| ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] cor[x_] := Apply[Times, ba[x]] Table[cor[DivisorSigma[2, w]], {w, 1, 100}]
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CROSSREFS
| Cf. A000213, A007947, A001157.
Sequence in context: A056496 A106367 A002791 * A017667 A001157 A002800
Adjacent sequences: A080396 A080397 A080398 * A080400 A080401 A080402
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Mar 19 2003
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