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 A229866 #6 Jul 23 2025 05:47:52 %S A229866 3,27,1215,384183,923742873,17451302074317,2658656027421822249 %N A229866 Number of n X n 0..2 arrays with corresponding row and column sums equal. %C A229866 Column 2 of A229870 %e A229866 Some solutions for n=4 %e A229866 ..0..0..1..2....0..1..2..1....0..0..2..2....0..1..0..0....0..0..1..1 %e A229866 ..1..1..1..0....2..2..0..2....2..1..0..0....0..2..0..1....1..2..0..1 %e A229866 ..0..2..1..0....2..2..1..0....2..2..0..0....1..0..2..1....1..0..0..2 %e A229866 ..2..0..0..2....0..1..2..2....0..0..2..1....0..0..2..1....0..2..2..1 %K A229866 nonn %O A229866 1,1 %A A229866 _R. H. Hardin_, Oct 01 2013