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 A352258 #10 Mar 17 2022 09:24:45 %S A352258 2,7,42,399,5614,112221,3102020,116076057,5774524092,376068483351, %T A352258 31643635513816,3401292647423655,462391295351625128, %U A352258 78801283167350942685,1775935516860530625139,230933325874558862792569 %N A352258 Number of symmetric binary n X n matrices with no 2 X 2 submatrix of all 1s. %C A352258 Equivalently, the number of labeled graphs (loops but not multiple edges allowed) with none of these subgraphs: 4-cycle, edge with a loop on each end, triangle with at least one loop. %Y A352258 Row sums of A350189. %Y A352258 Cf. A345249 (traceless matrices). %K A352258 nonn,hard %O A352258 1,1 %A A352258 _Brendan McKay_, Mar 09 2022