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 A066134 #17 Feb 23 2025 02:40:31
%S A066134 48,180,245,432,500,605,931,980,1200,1280,1620,1805,2205,2352,2420,
%T A066134 3380,3724,3888,3920,4500,4655,5445,5780,5808,6125,6845,7203,7220,
%U A066134 7936,8112,8379,8405,8820,9072,9251,9680,10580,10800,11520,11760,12500
%N A066134 Numbers from A066112 that are neither square nor twice a square, i.e., are not in A028982 but are in A028983.
%H A066134 Amiram Eldar, <a href="/A066134/b066134.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harry J. Smith)
%e A066134 180 is neither square nor twice a square, but sigma_4(180)/sigma_2(180) = 1135275414/49686 = 22849 = 73*313.
%t A066134 q[k_] := !IntegerQ[Sqrt[k]] && !IntegerQ[Sqrt[k/2]] && IntegerQ[r = DivisorSigma[4, k]/DivisorSigma[2, k]] && !PrimeQ[r]; Select[Range[12500], q] (* _Amiram Eldar_, Feb 23 2025 *)
%o A066134 (PARI) { n=0; for (m=1, 10^9, if (issquare(m) || issquare(m/2), next); if (frac(f=sigma(m, 4)/sigma(m, 2)), next); if (!isprime(f), write("b066134.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Feb 02 2010
%Y A066134 Cf. A001157, A001159, A028982, A028983, A046871, A066109, A066110, A066111, A066112.
%K A066134 nonn
%O A066134 1,1
%A A066134 _Labos Elemer_, Dec 06 2001