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 A140411 #16 Sep 12 2019 04:48:26
%S A140411 1,2,5,10,13,37,58,85,130
%N A140411 Conjectured complete list of squarefree numbers that can be written as a sum of at most two positive squares, but not as a sum of three positive squares.
%C A140411 Conjecture 1,9, p. 4, of Goswick et al. "The squarefree numbers in question form a subset of Euler's numeri idonei [A000926], therefore at most one number can be absent from the list above. If such a number does exist, it must exceed 2 * 10^11 and if it is even the Generalized Riemann Hypothesis is false."
%H A140411 Lee M. Goswick, Emil W. Kiss, Gabor Moussong, Nandor Simanyi, <a href="http://arxiv.org/abs/0806.3943">Sums of squares and orthogonal integral vectors</a>, arXiv:0806.3943 [math.NT], 2011-2013.
%H A140411 Daejun Kim, Jeongwon Lee, Byeong-Kweon Oh, <a href="https://arxiv.org/abs/1909.04982">A sum of three nonunit squares of integers</a>, arXiv:1909.04982 [math.NT], 2019.
%F A140411 a(n) in A005117 and a(n) in {i^2 + j^2 for i,j > 1} and a(n) not in {i^2 + j^2 + k^2 for i,j,k > 1}.
%t A140411 Join[{1},Select[Range[500], Abs[MoebiusMu[#]] == 1 && Length[Select[PowersRepresentations[#,2,2], Not[MemberQ[#, 0, 2]] &]] > 0 && Length[Select[PowersRepresentations[#,3,2], Not[MemberQ[#, 0, 2]] &]] == 0 &]] (* _Alonso del Arte_, Sep 12 2019 *)
%t A140411 Select[Range[500], SquareFreeQ[#] && (p = IntegerPartitions[#, {1, 3}, Range[Sqrt@#]^2]; p != {} && ! MemberQ[Length /@ p, 3]) &] (* _Giovanni Resta_, Sep 12 2019 *)
%Y A140411 Cf. A000926, A005117.
%K A140411 fini,full,nonn
%O A140411 1,2
%A A140411 _Jonathan Vos Post_, Jun 25 2008