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Search: id:A129087
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| 11025, 34155, 38745, 39585, 41895, 75735, 85995, 99225, 118755, 131355, 135135, 193725, 208845, 218025, 237195, 241395, 241605, 245385, 255645, 271215, 272745, 275625, 276885, 279279, 306495, 307125, 323505, 342225, 347985, 364455, 377685
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OFFSET
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1,1
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COMMENT
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This sequence contains the odd members of A125639, which (empirically) accounts for only about 0.08% of them.
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FORMULA
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Odd numbers k, such that both k and s(k) (A001065) are abundant (A005101)
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EXAMPLE
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The third odd number which is doubly abundant is 38745. Hence a(3)=38745
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MATHEMATICA
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s[n_]:=DivisorSigma[1, n]-n; DoublyAbundantNumberQ[k_]:=If[s[k]>k && s[s[k]]>s[k], True, False]; Select[Range[500000], OddQ[ # ] && DoublyAbundantNumberQ[ # ] & ]
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CROSSREFS
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Cf. A125639, A001065, A005101.
Adjacent sequences: A129084 A129085 A129086 this_sequence A129088 A129089 A129090
Sequence in context: A034712 A045152 A096930 this_sequence A139409 A032427 A094324
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KEYWORD
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easy,nonn
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AUTHOR
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Ant King (mathstutoring(AT)ntlworld.com), Apr 02 2007
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