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 A222651 #6 Jul 23 2025 02:52:21 %S A222651 1,7,60,724,7364,84816,927152,10585088,119198624,1364437632, %T A222651 15584195392,179262541056,2063988209152,23852186896896, %U A222651 276080500860416,3202923732204544,37215026284325888,433119059193262080 %N A222651 Number of nX2 0..3 arrays with no more than floor(nX2/2) elements equal to at least one king-move neighbor, with new values introduced in row major 0..3 order. %C A222651 Column 2 of A222654 %H A222651 R. H. Hardin, <a href="/A222651/b222651.txt">Table of n, a(n) for n = 1..210</a> %e A222651 Some solutions for n=3 %e A222651 ..0..1....0..1....0..0....0..0....0..0....0..1....0..1....0..1....0..1....0..1 %e A222651 ..2..2....2..2....0..1....1..0....1..2....0..0....2..0....2..3....0..2....2..1 %e A222651 ..0..1....1..2....2..3....2..3....0..3....2..3....3..0....1..0....3..0....3..1 %K A222651 nonn %O A222651 1,2 %A A222651 _R. H. Hardin_ Feb 27 2013