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Search: id:A023196
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| A023196 |
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Numbers n such that sigma(n) >= 2n (union of perfect (A000396) and abundant (A005101) numbers). |
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+0
13
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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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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These are the non-deficient numbers.
Comment from Max Alekseyev (maxale(AT)gmail.com), Jan 26 2005: The sequence of n that give local minima for A004125, i.e. such that A004125(n-1)>A004125(n) and A004125(n)<A004125(n+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 minima.
Also union of pseudoperfect and weird numbers. Cf. A005835, A006037. - Frank Adams-Watters (FrankTAW(AT)Netscape.net), Mar 29 2006
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
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If n is a member so is every positive multiple of n. The "primitive" members form A006039.
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MATHEMATICA
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Flatten[Table[If[DivisorSigma[1, n] >= 2*n, n, {}], {n, 1, 300}]] - Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Sep 18 2008
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CROSSREFS
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Cf. A004125, A006039, A000396, A005101.
Sequence in context: A051774 A119357 A097216 this_sequence A005835 A007620 A100715
Adjacent sequences: A023193 A023194 A023195 this_sequence A023197 A023198 A023199
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KEYWORD
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nonn,nice
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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