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 A205587 #7 Jul 22 2025 18:56:39 %S A205587 12574,248940,6127845,147377704,3619876639,88339585116,2185708696857, %T A205587 53385992474116,1322383286558544,32335854186137718,800647385900917353, %U A205587 19592761418771490008,484877507851310339810,11872137202509501621294 %N A205587 Number of (n+1)X6 0..2 arrays with no 2X2 subblock having the same number of equal edges as its horizontal or vertical neighbors, and new values 0..2 introduced in row major order. %C A205587 Column 5 of A205590 %H A205587 R. H. Hardin, <a href="/A205587/b205587.txt">Table of n, a(n) for n = 1..210</a> %e A205587 Some solutions for n=4 %e A205587 ..0..0..1..2..2..1....0..1..0..2..1..1....0..0..1..2..0..0....0..1..0..1..0..0 %e A205587 ..0..0..1..0..2..0....1..1..2..2..0..0....1..0..2..0..0..0....2..1..1..2..2..0 %e A205587 ..2..1..0..0..1..2....0..2..0..1..2..1....1..2..0..0..0..2....1..0..2..2..2..1 %e A205587 ..1..2..0..0..1..0....2..1..0..0..0..2....2..1..0..0..1..2....2..2..0..1..1..2 %e A205587 ..0..0..2..0..2..1....0..0..1..2..0..1....2..0..1..1..2..2....1..2..1..0..2..2 %K A205587 nonn %O A205587 1,1 %A A205587 _R. H. Hardin_ Jan 29 2012