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 A203537 #7 Jun 02 2025 07:36:08 %S A203537 0,4,72,144,1840,10404,69920,490000,3317120,22524516,153723240, %T A203537 1044840976,7112904336,48420242116,329561076960,2243249071504, %U A203537 15269163209664,103931377966276,707427841294920,4815226903450896 %N A203537 Number of nX3 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1. %C A203537 Column 3 of A203542 %H A203537 R. H. Hardin, <a href="/A203537/b203537.txt">Table of n, a(n) for n = 1..210</a> %F A203537 Empirical: a(n) = 7*a(n-1) -8*a(n-3) -38*a(n-4) +218*a(n-5) +400*a(n-6) -2936*a(n-7) +609*a(n-8) -2791*a(n-9) +4072*a(n-10) +248*a(n-11) -588*a(n-12) +4916*a(n-13) -1912*a(n-14) +8920*a(n-15) -7799*a(n-16) +3393*a(n-17) -5960*a(n-18) -464*a(n-19) -238*a(n-20) +18*a(n-21) -56*a(n-22) -9*a(n-24) -a(n-25) %e A203537 Some solutions for n=5 %e A203537 ..1..1..2....2..0..0....0..1..2....0..1..0....0..1..1....2..1..0....2..0..1 %e A203537 ..0..0..0....1..1..1....0..1..0....0..1..0....0..0..0....0..1..0....1..0..1 %e A203537 ..1..2..1....0..1..1....2..1..0....2..2..1....1..0..0....0..0..1....1..2..1 %e A203537 ..1..0..1....0..0..0....0..1..0....1..0..1....1..1..1....1..0..1....0..0..0 %e A203537 ..2..0..1....1..1..1....0..1..2....1..0..1....0..0..1....1..0..0....2..1..1 %K A203537 nonn %O A203537 1,2 %A A203537 _R. H. Hardin_ Jan 02 2012