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Search: id:A057654
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| A057654 |
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Numbers n such that sigma(n)^2-phi(n)^2 is a perfect square. |
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+0
1
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| 1, 95, 99, 146, 323, 377, 1095, 1102, 1351, 1368, 1630, 1919, 1943, 2261, 2639, 2743, 3915, 4607, 4743, 5042, 5045, 5183, 5249, 6347, 6497, 7389, 8265, 8307, 8749, 9407, 9701
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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sigma(95)^2-phi(95)^2 = 120^2 - 72^2 = 96^2, so 95 is a term of the sequence.
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MATHEMATICA
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Select[Range[10^4], IntegerQ[Sqrt[DivisorSigma[1, # ]^2 - EulerPhi[ # ]^2]] &]
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CROSSREFS
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Sequence in context: A033415 A067266 A055467 this_sequence A046005 A045121 A057874
Adjacent sequences: A057651 A057652 A057653 this_sequence A057655 A057656 A057657
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KEYWORD
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easy,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 12 2002
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