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A080402
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A001157(n) is not squarefree: sum of squares of divisors of n is not squarefree.
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2
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6, 7, 14, 15, 21, 24, 26, 27, 28, 30, 33, 34, 35, 36, 39, 41, 42, 43, 45, 46, 51, 54, 55, 56, 57, 60, 63, 65, 66, 69, 70, 74, 77, 78, 81, 82, 84, 85, 86, 87, 90, 91, 93, 94, 95, 96, 100, 102, 104, 105, 106, 107, 108, 110, 111, 112, 114, 115, 119, 120, 123, 125, 126, 129
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
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FORMULA
| mu[sigma[2, a(n)]]=0.
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MATHEMATICA
| Do[s=MoebiusMu[DivisorSigma[2, n]]; If[Equal[s, 0], Print[n]], {n, 1, 1000}]
Select[Range[130], !SquareFreeQ[DivisorSigma[2, #]]&] (* From Harvey P. Dale, Oct 10 2011 *)
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CROSSREFS
| Cf. A001157, A065300, A080401.
Sequence in context: A041999 A041319 A042315 * A146308 A047589 A125996
Adjacent sequences: A080399 A080400 A080401 * A080403 A080404 A080405
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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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