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 A269147 #4 Feb 20 2016 07:16:01 %S A269147 24,768,13904,220968,3277728,46576336,642676704,8680278136, %T A269147 115349343264,1513379596864,19651887694240,253030595298696, %U A269147 3234828051983328,41105657832397744,519625334069189984,6539008095907322520 %N A269147 Number of nX3 0..3 arrays with some element plus some horizontally, antidiagonally or vertically adjacent neighbor totalling three exactly once. %C A269147 Column 3 of A269152. %H A269147 R. H. Hardin, <a href="/A269147/b269147.txt">Table of n, a(n) for n = 1..210</a> %F A269147 Empirical: a(n) = 26*a(n-1) -199*a(n-2) +408*a(n-3) -463*a(n-4) +322*a(n-5) -141*a(n-6) +36*a(n-7) -4*a(n-8) for n>9 %e A269147 Some solutions for n=3 %e A269147 ..0..2..3. .0..1..1. .3..1..0. .2..2..3. .0..0..3. .0..0..1. .3..2..2 %e A269147 ..0..0..2. .3..1..0. .1..0..1. .2..2..3. .0..2..2. .1..0..0. .3..3..3 %e A269147 ..1..0..2. .1..0..2. .0..0..2. .0..2..1. .2..3..2. .0..1..3. .1..2..2 %Y A269147 Cf. A269152. %K A269147 nonn %O A269147 1,1 %A A269147 _R. H. Hardin_, Feb 20 2016