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 A203486 #7 Jul 22 2025 17:16:51 %S A203486 12,80,624,3760,25002,171068,1107888,7411872,50469114,335270710, %T A203486 2266967088,15497479060,104719636176,715192200880,4919017621164, %U A203486 33647413101184,231673960276602,1602349695229334,11054192845643568 %N A203486 Number of nX3 0..2 arrays with row sums equal and column sums unequal to adjacent columns. %C A203486 Column 3 of A203491 %H A203486 R. H. Hardin, <a href="/A203486/b203486.txt">Table of n, a(n) for n = 1..106</a> %e A203486 Some solutions for n=5 %e A203486 ..0..0..1....1..2..2....1..1..0....2..1..0....2..1..2....1..1..0....1..0..2 %e A203486 ..0..1..0....2..1..2....1..1..0....2..1..0....1..2..2....0..1..1....2..1..0 %e A203486 ..0..1..0....2..2..1....1..1..0....2..1..0....1..2..2....2..0..0....2..0..1 %e A203486 ..0..1..0....2..1..2....0..0..2....0..1..2....1..2..2....0..2..0....2..0..1 %e A203486 ..1..0..0....2..1..2....2..0..0....0..1..2....1..2..2....2..0..0....2..1..0 %K A203486 nonn %O A203486 1,1 %A A203486 _R. H. Hardin_ Jan 02 2012