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 A269203 #10 May 27 2025 16:40:08 %S A269203 64,1740,25572,400428,5877228,84310620,1184381844,16385570076, %T A269203 223935582828,3030348558252,40673437553748,542180347359564, %U A269203 7185077761974828,94737850175764476,1243661129422894356,16262904060512571516,211935250795961093868,2753454797480878594380 %N A269203 Number of 3 X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three no more than once. %H A269203 R. H. Hardin, <a href="/A269203/b269203.txt">Table of n, a(n) for n = 1..210</a> %F A269203 Empirical: a(n) = 24*a(n-1) -130*a(n-2) -248*a(n-3) +935*a(n-4) +272*a(n-5) -1768*a(n-6) +960*a(n-7) -144*a(n-8). %e A269203 Some solutions for n=3: %e A269203 ..1..3..3. .1..3..1. .1..2..0. .0..0..0. .2..0..3. .1..1..1. .3..3..3 %e A269203 ..3..1..1. .2..3..2. .3..1..0. .0..1..1. .1..3..1. .3..1..3. .3..3..3 %e A269203 ..1..1..3. .2..3..1. .3..2..0. .3..3..3. .2..0..1. .1..2..0. .2..3..1 %Y A269203 Row 3 of A269201. %K A269203 nonn %O A269203 1,1 %A A269203 _R. H. Hardin_, Feb 20 2016