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 A208386 #9 Jul 22 2025 21:18:57 %S A208386 1,14,3042,5800644,93120350760,12599441934740388, %T A208386 14365030966055594634024,138014735764906572120867370968, %U A208386 11173919983811965361047734248948606160,7623374241518340770502859232163385538378521776 %N A208386 Number of n X n 0..2 arrays with new values 0..2 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors. %C A208386 Diagonal of A208392 %H A208386 R. H. Hardin, <a href="/A208386/b208386.txt">Table of n, a(n) for n = 1..13</a> %e A208386 Some solutions for n=4 %e A208386 ..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..1..0..2 %e A208386 ..1..1..0..2....0..1..0..2....0..1..1..0....0..1..2..0....1..2..2..1 %e A208386 ..2..0..1..0....2..0..1..2....0..1..0..2....1..2..2..0....1..0..1..1 %e A208386 ..1..2..0..2....0..2..1..0....2..2..0..1....0..1..1..2....0..0..2..0 %K A208386 nonn %O A208386 1,2 %A A208386 _R. H. Hardin_ Feb 25 2012