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 A275500 #4 Jul 30 2016 19:55:19 %S A275500 14,324,400,656,988,2628,7140,19368,52864,144228,394248,1077956, %T A275500 2947432,8062396,22050256,60314412,164976924,451256880,1234335036, %U A275500 3376282048,9235192524,25261198432,69097304872,189003117812,516983415672 %N A275500 Number of nX4 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,0) or (-1,-1) and new values introduced in order 0..2. %C A275500 Column 4 of A275504. %H A275500 R. H. Hardin, <a href="/A275500/b275500.txt">Table of n, a(n) for n = 1..210</a> %F A275500 Empirical: a(n) = a(n-1) +8*a(n-2) -28*a(n-4) -9*a(n-5) +55*a(n-6) +16*a(n-7) -70*a(n-8) -9*a(n-9) +56*a(n-10) -28*a(n-12) +a(n-13) +8*a(n-14) -a(n-16) for n>20 %e A275500 Some solutions for n=4 %e A275500 ..0..0..0..1. .0..1..1..0. .0..0..1..2. .0..0..1..2. .0..0..1..2 %e A275500 ..2..2..1..1. .1..2..0..0. .0..1..2..0. .0..1..2..2. .2..1..2..2 %e A275500 ..2..1..1..2. .2..2..0..2. .1..1..2..0. .1..1..2..0. .1..1..2..0 %e A275500 ..1..1..0..2. .0..0..1..1. .2..2..0..1. .2..2..0..0. .0..0..0..1 %Y A275500 Cf. A275504. %K A275500 nonn %O A275500 1,1 %A A275500 _R. H. Hardin_, Jul 30 2016