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 A222373 #6 Jul 23 2025 02:32:38 %S A222373 1,1,5,18,63,234,1163,4953,24021,109395,536457,2526558,12324313, %T A222373 59135699,288057673,1396084937,6800380165,33152287976,161670473265, %U A222373 790996243845,3863624579433,18948369852560,92716137764021,455475835479225 %N A222373 Number of nX2 0..3 arrays with no more than floor(nX2/2) elements unequal to at least one horizontal or vertical neighbor, with new values introduced in row major 0..3 order. %C A222373 Column 2 of A222378 %H A222373 R. H. Hardin, <a href="/A222373/b222373.txt">Table of n, a(n) for n = 1..210</a> %e A222373 Some solutions for n=4 %e A222373 ..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..1 %e A222373 ..0..1....0..0....0..0....1..0....0..0....0..0....0..0....0..0....1..1....2..2 %e A222373 ..0..0....0..0....1..0....1..1....0..1....0..0....0..0....0..1....1..1....2..2 %e A222373 ..0..0....0..0....1..1....1..1....0..0....1..1....0..1....1..1....1..1....2..2 %K A222373 nonn %O A222373 1,3 %A A222373 _R. H. Hardin_ Feb 17 2013