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%I #7 Mar 09 2014 05:02:34
%S 1,2,4,6,8,10,16,18,20,28,32,44,50,52,64,70,88,104,110,128,130,136,
%T 152,174,184,186,196,222,232,246,256,258,272,282,304,315,318,354,366,
%U 368,402,426,438,464,474,496,498,512,534,550,582,592,606,618,642,650,654
%N Numbers n such that abs(sigma(n) - 2n) <= sqrt(n).
%C Abundance-radius = abs(sigma(n)-2n) does not exceed square root.
%H Charles R Greathouse IV, <a href="/A088007/b088007.txt">Table of n, a(n) for n = 1..10000</a>
%t abu[x_] := Abs[DivisorSigma[1, x]-2*x] Do[If[ !Greater[abu[n], Sqrt[n]//N], Print[n]], {n, 1, 100000}]
%o (PARI) is(n)=abs(sigma(n)-2*n)<=sqrtint(n) \\ _Charles R Greathouse IV_, Mar 09 2014
%Y Cf. A077374, A088008-A088012, A000396, A000079, A005100, A005101.
%K nonn
%O 1,2
%A _Labos Elemer_, Oct 20 2003
%E New name from _Charles R Greathouse IV_, Mar 09 2014