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 A203559 #7 Jul 22 2025 17:20:28 %S A203559 3,9,87,177,993,10833,35619,219873,2083713,8710539,55644339,473819481, %T A203559 2320792659,15120204297,119105713827,650725327233,4293779332929, %U A203559 32065818855387,188739799967427,1256510215733187,9061494550445907 %N A203559 Number of nX3 0..2 arrays with row sums equal and column sums equal. %C A203559 Column 3 of A203564 %H A203559 R. H. Hardin, <a href="/A203559/b203559.txt">Table of n, a(n) for n = 1..122</a> %e A203559 Some solutions for n=5 %e A203559 ..1..0..2....2..0..1....1..2..0....2..1..0....2..2..2....2..0..1....0..2..1 %e A203559 ..0..1..2....0..2..1....2..1..0....2..1..0....2..2..2....1..0..2....2..1..0 %e A203559 ..2..0..1....0..1..2....1..1..1....0..2..1....2..2..2....0..1..2....1..1..1 %e A203559 ..1..2..0....2..0..1....0..1..2....0..1..2....2..2..2....1..2..0....0..1..2 %e A203559 ..1..2..0....1..2..0....1..0..2....1..0..2....2..2..2....1..2..0....2..0..1 %K A203559 nonn %O A203559 1,1 %A A203559 _R. H. Hardin_ Jan 03 2012