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Odd numbers n such that abs(sigma(n)-2n) <= sqrt(n). Abundance-radius = abs(sigma(n)-2n) does not exceed square root of n and n is odd.
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%I #9 Nov 09 2013 20:10:36

%S 1,315,945,1155,2205,7425,8415,8925,9405,9555,24885,26145,26325,28035,

%T 30555,31815,32445,33705,34335,35595,40005,40365,41265,43155,46035,

%U 49875,51765,55335,78975,80535,83265,91455,96915,101475,106425,130815,191565,338415

%N Odd numbers n such that abs(sigma(n)-2n) <= sqrt(n). Abundance-radius = abs(sigma(n)-2n) does not exceed square root of n and n is odd.

%H Donovan Johnson, <a href="/A087415/b087415.txt">Table of n, a(n) for n = 1..1000</a>

%t abu[x_] := Abs[DivisorSigma[1, x]-2*x] Do[If[ !Greater[abu[n], Sqrt[n]//N]&& OddQ[n], Print[n]], {n, 1, 100000}]

%Y Cf. A077374, A088007-A088012, A000396, A000079, A005100, A005101.

%K nonn

%O 1,2

%A _Labos Elemer_, Oct 20 2003