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 A333740 #10 May 02 2022 09:49:14 %S A333740 1,1,2,7,194,601055,294494683312,14584161564179926207, %T A333740 80055722734531008786502722278, %U A333740 53505113579082591021525466231199449015539 %N A333740 Number of inequivalent 2n X 2n binary matrices with rows and columns summing to n, where equivalence means permutations of rows or columns. %H A333740 <a href="/index/Mat#binmat">Index entries for sequences related to binary matrices</a> %H A333740 <a href="/index/Mat#inequiv">Index to number of inequivalent matrices modulo permutation of rows and columns</a> %F A333740 a(n) = A133687(2n,n). %Y A333740 Cf. A133687. %K A333740 nonn,more %O A333740 0,3 %A A333740 _Alois P. Heinz_, Apr 03 2020