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A080401
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A001157(n) is squarefree: sum of squares of divisors of n is squarefree.
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2
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1, 2, 3, 4, 5, 8, 9, 10, 11, 12, 13, 16, 17, 18, 19, 20, 22, 23, 25, 29, 31, 32, 37, 38, 40, 44, 47, 48, 49, 50, 52, 53, 58, 59, 61, 62, 64, 67, 68, 71, 72, 73, 75, 76, 79, 80, 83, 88, 89, 92, 97, 98, 99, 101, 103, 109, 113, 116, 117, 118, 121, 122, 124, 127, 128, 131, 137
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| Abs[mu[sigma[2, a(n)]]]=1.
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MATHEMATICA
| Do[s=MoebiusMu[DivisorSigma[2, n]]; If[ !Equal[s, 0], Print[n]], {n, 1, 1000}]
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CROSSREFS
| Cf. A001157, A065300.
Sequence in context: A047602 A039076 A037471 * A180734 A031482 A047369
Adjacent sequences: A080398 A080399 A080400 * A080402 A080403 A080404
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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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