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 A203540 #7 Jun 02 2025 07:36:22 %S A203540 0,196,10404,614656,46485124,3743237124,257720706244,20056281523776, %T A203540 1492411644481536,112070612773938064,8426586286656023616, %U A203540 632681292075367516804,47524857928919914127524,3570176077491731508417600 %N A203540 Number of nX6 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1. %C A203540 Column 6 of A203542 %H A203540 R. H. Hardin, <a href="/A203540/b203540.txt">Table of n, a(n) for n = 1..73</a> %e A203540 Some solutions for n=5 %e A203540 ..2..1..0..2..0..0....2..0..0..0..1..1....2..0..0..0..0..0....0..0..0..1..1..0 %e A203540 ..0..1..0..1..1..1....1..1..1..1..2..0....1..1..1..1..1..1....1..1..2..0..1..0 %e A203540 ..0..2..2..0..1..2....0..1..2..0..0..0....0..2..0..2..1..1....0..2..2..0..1..1 %e A203540 ..1..0..1..0..1..0....0..2..0..1..1..1....0..0..0..0..0..0....0..0..1..2..0..1 %e A203540 ..1..0..1..1..1..0....1..1..0..0..0..1....1..1..1..1..1..0....1..1..1..0..0..1 %K A203540 nonn %O A203540 1,2 %A A203540 _R. H. Hardin_ Jan 02 2012