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 A275223 #4 Jul 20 2016 18:24:41 %S A275223 5,36,61,187,648,2282,8134,29027,103456,368889,1315431,4690476, %T A275223 16725240,59638892,212660009,758302172,2703951339,9641739667, %U A275223 34380480348,122593793026,437144505226,1558768299519,5558250385696,19819589184889 %N A275223 Number of nX3 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,1) or (-1,0) and new values introduced in order 0..2. %C A275223 Column 3 of A275228. %H A275223 R. H. Hardin, <a href="/A275223/b275223.txt">Table of n, a(n) for n = 1..210</a> %F A275223 Empirical: a(n) = 3*a(n-1) +5*a(n-2) -10*a(n-3) -a(n-4) -10*a(n-5) +21*a(n-6) -4*a(n-7) -4*a(n-8) +a(n-9) for n>13 %e A275223 Some solutions for n=4 %e A275223 ..0..0..1. .0..1..0. .0..1..1. .0..1..2. .0..0..1. .0..1..1. .0..1..2 %e A275223 ..2..1..2. .2..2..1. .2..0..2. .1..2..1. .1..1..2. .2..0..2. .2..0..1 %e A275223 ..1..2..1. .0..1..0. .0..2..0. .0..1..0. .2..2..1. .0..2..0. .0..1..2 %e A275223 ..2..1..0. .1..0..1. .1..0..1. .1..2..1. .0..0..2. .2..0..2. .1..0..1 %Y A275223 Cf. A275228. %K A275223 nonn %O A275223 1,1 %A A275223 _R. H. Hardin_, Jul 20 2016