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 A222900 #6 Jul 23 2025 03:13:53 %S A222900 1,4,14,75,411,2522,15919,103627,683480,4554799,30542304,205785953, %T A222900 1391485044,9436529666,64150640719,437015936703,2982527052975, %U A222900 20387828050502,139566607631735,956650211233825,6564964362464004 %N A222900 Number of nX2 0..3 arrays with no more than floor(nX2/2) elements unequal to at least one horizontal or antidiagonal neighbor, with new values introduced in row major 0..3 order. %C A222900 Column 2 of A222906 %H A222900 R. H. Hardin, <a href="/A222900/b222900.txt">Table of n, a(n) for n = 1..210</a> %e A222900 Some solutions for n=3 %e A222900 ..0..0....0..0....0..1....0..0....0..1....0..0....0..0....0..1....0..0....0..0 %e A222900 ..1..2....0..0....1..1....0..1....0..0....0..1....0..0....2..2....1..0....0..0 %e A222900 ..2..2....0..0....1..1....0..0....0..0....1..1....1..2....2..2....0..0....1..0 %K A222900 nonn %O A222900 1,2 %A A222900 _R. H. Hardin_ Mar 09 2013