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 A183578 #7 Jun 22 2022 11:42:14 %S A183578 2,78,814,9667,110674,1282814,14823037,171459557,1982720806, %T A183578 22929915669,265174801858,3066662593835,35464903052433, %U A183578 410139828611289,4743130059530921,54852719114258196,634353415473617224 %N A183578 Half the number of n X 3 0..3 arrays with each element equal to either the maximum or the minimum of its horizontal and vertical neighbors. %C A183578 Column 3 of A183584. %H A183578 R. H. Hardin, <a href="/A183578/b183578.txt">Table of n, a(n) for n = 1..200</a> %e A183578 Some solutions with a(1,1)<=1 for 5 X 3 %e A183578 ..0..0..0....1..0..0....0..0..2....1..0..0....0..0..3....0..1..1....1..0..1 %e A183578 ..0..3..3....1..1..0....0..2..2....1..1..1....0..0..3....0..0..0....1..0..1 %e A183578 ..1..0..0....0..0..2....2..1..2....3..0..0....3..3..3....2..2..0....1..0..0 %e A183578 ..1..1..1....0..0..2....2..1..1....3..0..0....2..2..3....0..0..0....0..1..0 %e A183578 ..0..0..1....0..1..1....1..1..1....3..0..0....2..2..2....0..1..1....0..1..0 %Y A183578 Cf. A183584. %K A183578 nonn %O A183578 1,1 %A A183578 _R. H. Hardin_, Jan 05 2011