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%I #13 Jun 18 2018 18:39:51
%S 1,4,529,2116,2583,3249,3346,6150,10332,12474,12792,12996,28224,38240,
%T 59245,85905,91035,103607,142560,176382,212949,236980,249744,343620,
%U 360096,364140,379050,414428,450840,751530,787710,788424,851796,1059474,1132096,1366407
%N Numbers n such that sigma_2(n)*sigma_1(n)/sigma_0(n) is a perfect square.
%H Donovan Johnson, <a href="/A152218/b152218.txt">Table of n, a(n) for n = 1..200</a>
%F {n: A001157(n)*A000203(n)/A000005(n) in A000290}.
%t fQ[n_] := IntegerQ[ Sqrt[ DivisorSigma[2, n] DivisorSigma[1, n]/DivisorSigma[0, n]]]; k = 1; lst = {}; While[k < 1132096, If[ fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst (* _Robert G. Wilson v_, Sep 10 2010 *)
%t Select[Range[137*10^4],IntegerQ[Sqrt[(DivisorSigma[2,#]DivisorSigma[ 1,#])/ DivisorSigma[ 0,#]]]&] (* _Harvey P. Dale_, Jun 18 2018 *)
%Y Cf. A000005, A001157, A000203, A140480.
%K nonn
%O 1,2
%A _Ctibor O. Zizka_, Nov 29 2008
%E Correct definition recovered by _Jack Brennen_
%E 12 more terms from _R. J. Mathar_, Aug 25 2010
%E More terms from _Robert G. Wilson v_, Sep 10 2010
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