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 A133206 #8 Sep 18 2020 23:17:38
%S A133206 1,1,3,7,25,99,690,6551,133174,4138641,290045659
%N A133206 Number of unlabeled graphs with n nodes and a degenerate adjacency matrix.
%C A133206 a(n) = A000088(n) - A109717(n)
%H A133206 Ali Sltan Ali AL-Tarimshawy, J. Siemons, <a href="https://arxiv.org/abs/2006.12875">Singular Graphs with Dihedral Group Action</a>, arXiv:2006.12875 [math.CO], 2020.
%t A133206 k = {}; For[i = 1, i < 8, i++, lg = ListGraphs[i] ; len = Length[lg]; k = Append[k, Length[Select[Range[len], Det[ToAdjacencyMatrix[lg[[ # ]]]] == 0 &]]]]; k
%Y A133206 Cf. A000088, A109717.
%K A133206 more,nonn
%O A133206 1,3
%A A133206 _Tanya Khovanova_, Aug 27 2008