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A023196
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Nondeficient numbers: numbers k such that sigma(k) >= 2k; union of A000396 and A005101.
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61
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6, 12, 18, 20, 24, 28, 30, 36, 40, 42, 48, 54, 56, 60, 66, 70, 72, 78, 80, 84, 88, 90, 96, 100, 102, 104, 108, 112, 114, 120, 126, 132, 138, 140, 144, 150, 156, 160, 162, 168, 174, 176, 180, 186, 192, 196, 198, 200, 204, 208, 210, 216, 220, 222, 224, 228, 234, 240, 246, 252
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OFFSET
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1,1
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COMMENTS
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Also called the non-deficient numbers.
If k is a term, so is every positive multiple of k. The "primitive" terms form A006039.
The sequence of numbers k that give local minima for A004125, i.e., such that A004125(k-1) > A004125(k) and A004125(k) < A004125(k+1) coincides with this sequence for the first 1014 terms. Then there appears 4095 which is a term of A023196 but is not a local minimum. - Max Alekseyev, Jan 26 2005
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LINKS
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MAPLE
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MATHEMATICA
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Select[Range[300], DivisorSigma[1, #] >= 2# &] (* Harvey P. Dale, Sep 26 2014 *)
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PROG
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(GAP) Filtered([1..260], n->Sigma(n)>=2*n); # Muniru A Asiru, Dec 04 2018
(Magma) [n: n in [1..300] | not (2*n gt DivisorSigma(1, n))]; // Vincenzo Librandi, Dec 05 2018
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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STATUS
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approved
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