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 A222909 #6 Jul 23 2025 03:14:49 %S A222909 15,75,767,7794,101398,1346067,21064292,356150811,6366063573, %T A222909 115668702638,2139261596454,39572902785373,737955955427551, %U A222909 13730713590038976,256798310856319397,4793531311138014167 %N A222909 Number of 4Xn 0..3 arrays with no more than floor(4Xn/2) elements unequal to at least one horizontal or antidiagonal neighbor, with new values introduced in row major 0..3 order. %C A222909 Row 4 of A222906 %H A222909 R. H. Hardin, <a href="/A222909/b222909.txt">Table of n, a(n) for n = 1..31</a> %e A222909 Some solutions for n=3 %e A222909 ..0..1..1....0..1..1....0..1..1....0..0..0....0..0..0....0..0..0....0..1..2 %e A222909 ..1..1..1....1..1..2....1..1..1....0..0..1....0..0..0....0..0..1....1..1..1 %e A222909 ..1..1..1....0..1..1....1..1..1....2..3..3....1..0..0....2..2..0....1..1..1 %e A222909 ..2..1..1....1..1..1....2..2..2....2..3..3....0..0..2....2..2..2....1..1..3 %K A222909 nonn %O A222909 1,1 %A A222909 _R. H. Hardin_ Mar 09 2013