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Search: id:A069085
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| A069085 |
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Abundant numbers n such that n = sigma(k) - 2k, where k = sigma(n) - 2n. |
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2
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OFFSET
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1,1
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COMMENT
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All triply perfect numbers (A005820) are in the sequence, as are 45840 and 51168. Are there any other terms?
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EXAMPLE
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sigma(45840) - 2*45840 = 51168 and sigma(51168) - 2*51168 = 45840, so 45840 and 51168 are in the sequence.
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MATHEMATICA
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For[n=1, True, n++, k=DivisorSigma[1, n]-2n; If[k>0&&DivisorSigma[1, k]-2k==n, Print[n]]]
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CROSSREFS
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Cf. A005820.
Adjacent sequences: A069082 A069083 A069084 this_sequence A069086 A069087 A069088
Sequence in context: A090216 A113546 A114887 this_sequence A039688 A005820 A052787
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KEYWORD
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more,nonn
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AUTHOR
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Naohiro Nomoto (n_nomoto(AT)yabumi.com), Apr 05 2002
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EXTENSIONS
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Edited by Dean Hickerson (dean(AT)math.ucdavis.edu), Apr 11 2002
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