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%I #19 Dec 05 2013 09:10:48
%S 27720,30240,32760,50400,55440,60480,65520,75600,83160,85680,90720,
%T 95760,98280,100800,105840,110880,115920,120120,120960,128520,131040,
%U 138600,141120,143640,151200,163800,166320,171360,176400,180180,181440,184800,191520,194040
%N Numbers with abundancy 4 <= sigma(n)/n < 5.
%C A subsequence of A023198 (numbers with abundancy >= 4). It differs from A023198 from a(31093) on: The term A023198(31093) = 122522400 = A023199(5) = A215264(1) is not in this sequence. It excludes all terms of A215264, but also the 5-perfect numbers A046060, which are neither in this sequence nor in A215264. [Corrected by _M. F. Hasler_, Dec 05 2013]
%C A108775(a(n)) = 4.
%C There are 31092 terms less than 122522399. - _T. D. Noe_, Dec 04 2013
%H Jaroslav Krizek, <a href="/A230608/b230608.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Abundancy.html">Abundancy</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AbundantNumber.html">Abundant Number</a>
%e 27720 is in sequence because sigma(27720) / 27720 = 112320 / 27720 = 4.0519....
%t Select[Range[200000], 4 <= DivisorSigma[1, #]/# < 5 &] (* _T. D. Noe_, Dec 04 2013 *)
%Y Cf. A000203, A023198, A023199, A108775.
%Y Cf. A005100 (deficient numbers with abundancy 1 <= a < 2),
%Y Cf. A204829 (numbers with abundancy 2 <= a < 3),
%Y Cf. A204828 (abundant numbers with abundancy 3 <= a < 4).
%Y Cf. A215264 (abundant numbers with abundancy > 5).
%K nonn
%O 1,1
%A _Jaroslav Krizek_, Nov 29 2013
%E Corrected and edited by _M. F. Hasler_, Dec 05 2013
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