This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A152218 #22 Feb 01 2025 08:42:51
%S A152218 1,4,529,2116,2583,3249,3346,6150,10332,12474,12792,12996,28224,38240,
%T A152218 59245,85905,91035,103607,142560,176382,212949,236980,249744,343620,
%U A152218 360096,364140,379050,414428,450840,751530,787710,788424,851796,1059474,1132096,1366407
%N A152218 Numbers k such that sigma_2(k)*sigma_1(k)/sigma_0(k) is a perfect square.
%H A152218 Amiram Eldar, <a href="/A152218/b152218.txt">Table of n, a(n) for n = 1..500</a> (terms 1..200 from Donovan Johnson)
%F A152218 {k: A001157(k)*A000203(k)/A000005(k) in A000290}.
%t A152218 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 A152218 Select[Range[137*10^4],IntegerQ[Sqrt[(DivisorSigma[2,#]DivisorSigma[ 1,#])/ DivisorSigma[ 0,#]]]&] (* _Harvey P. Dale_, Jun 18 2018 *)
%o A152218 (PARI) isok(k) = {my(f = factor(k)); issquare(sigma(f, 2) * sigma(f) / numdiv(f));} \\ _Amiram Eldar_, Feb 01 2025
%Y A152218 Cf. A000005, A000290, A000203, A001157, A140480, A144695.
%K A152218 nonn
%O A152218 1,2
%A A152218 _Ctibor O. Zizka_, Nov 29 2008
%E A152218 Correct definition recovered by _Jack Brennen_
%E A152218 12 more terms from _R. J. Mathar_, Aug 25 2010
%E A152218 More terms from _Robert G. Wilson v_, Sep 10 2010