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 A222451 #6 Jul 23 2025 02:36:25 %S A222451 0,2,2,17,27,194,467,2375,6320,31706,84949,426134,1133626,5776492, %T A222451 15176513,78547862,204559282,1071259196,2775207035,14655072445, %U A222451 37875592694,201114091282,519500141148,2768445005172,7154712147158 %N A222451 Number of nX3 0..1 arrays with exactly floor(nX3/2) elements unequal to at least one horizontal, vertical or antidiagonal neighbor, with new values introduced in row major 0..1 order. %C A222451 Column 3 of A222456 %H A222451 R. H. Hardin, <a href="/A222451/b222451.txt">Table of n, a(n) for n = 1..210</a> %e A222451 Some solutions for n=4 %e A222451 ..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0 %e A222451 ..0..0..0....0..1..1....0..0..1....0..0..0....1..1..1....0..0..0....0..0..0 %e A222451 ..0..0..0....1..1..1....0..1..1....1..1..1....1..1..1....0..0..0....0..0..1 %e A222451 ..1..1..1....1..1..1....1..1..1....1..1..1....1..1..1....1..0..1....1..1..1 %K A222451 nonn %O A222451 1,2 %A A222451 _R. H. Hardin_ Feb 20 2013