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 A229867 #6 Jul 23 2025 05:47:58 %S A229867 4,64,8704,15106048,354003288064,115737559589453824, %T A229867 542277543422445827915776 %N A229867 Number of n X n 0..3 arrays with corresponding row and column sums equal. %C A229867 Column 3 of A229870 %e A229867 Some solutions for n=4 %e A229867 ..0..0..2..2....0..2..0..2....0..0..2..2....0..2..0..0....0..2..2..0 %e A229867 ..2..1..0..2....0..0..2..0....0..2..3..2....2..3..3..0....2..1..1..0 %e A229867 ..1..2..1..2....3..0..2..1....3..2..1..1....0..0..1..3....2..0..3..2 %e A229867 ..1..2..3..2....1..0..2..0....1..3..1..0....0..3..0..0....0..1..1..1 %K A229867 nonn %O A229867 1,1 %A A229867 _R. H. Hardin_, Oct 01 2013