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 A230670 #11 Feb 09 2018 11:08:35 %S A230670 3,87,1173,17271,251595,3669765,53519163,780527655,11383251453, %T A230670 166013909415,2421155095347,35310246222069,514966385300499, %U A230670 7510295349852327,109530520538219973,1597398553655896551 %N A230670 Number of n X 3 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value 2-x(i,j). %C A230670 Column 3 of A230675. %H A230670 R. H. Hardin, <a href="/A230670/b230670.txt">Table of n, a(n) for n = 1..210</a> %F A230670 Empirical: a(n) = 14*a(n-1) +9*a(n-2) -9*a(n-3) +30*a(n-4) -19*a(n-5). %F A230670 Empirical g.f.: 3*x*(1 + 15*x - 24*x^2 + 31*x^3 - 21*x^4) / (1 - 14*x - 9*x^2 + 9*x^3 - 30*x^4 + 19*x^5). - _Colin Barker_, Feb 09 2018 %e A230670 Some solutions for n=3: %e A230670 ..2..0..1....1..0..2....0..1..1....0..2..2....0..2..0....1..1..2....2..0..1 %e A230670 ..1..1..0....1..1..0....1..2..1....2..0..2....1..0..2....1..0..2....2..1..1 %e A230670 ..0..2..0....1..2..1....0..1..0....0..2..2....2..1..1....0..2..0....2..0..2 %K A230670 nonn %O A230670 1,1 %A A230670 _R. H. Hardin_, Oct 27 2013