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Search: id:A137210
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| A137210 |
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Numbers n such that abundance(n) = abundance(sigma(n)). |
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+0
1
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OFFSET
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1,2
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EXAMPLE
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abundance(84) = sigma(84) - 2(84) = 56 = abundance(224) = abundance(sigma(84)), so 84 is a term in the sequence.
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MATHEMATICA
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abund[n_] := DivisorSigma[1, n]-2n; l = {}; For[i = 1, i <= 10^6, i++, If[abund[i] == abund[DivisorSigma[1, i]], l = Append[l, i]]]; l
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CROSSREFS
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Adjacent sequences: A137207 A137208 A137209 this_sequence A137211 A137212 A137213
Sequence in context: A135804 A112066 A096383 this_sequence A131072 A083986 A064198
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Mar 05 2008
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EXTENSIONS
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a(7) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 27 2008
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