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 A276249 #6 Jun 07 2021 13:37:11 %S A276249 5,36,85,279,900,2837,9148,29570,95102,306540,989092,3188130,10278456, %T A276249 33146672,106872610,344585885,1111106822,3582609009,11551580944, %U A276249 37246820838,120097695423,387239261828,1248605509417,4025972358284 %N A276249 Number of 3 X n 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,1) or (0,-2) and new values introduced in order 0..2. %C A276249 Row 3 of A276248. %H A276249 R. H. Hardin, <a href="/A276249/b276249.txt">Table of n, a(n) for n = 1..210</a> %F A276249 Empirical: a(n) = 2*a(n-1) +3*a(n-2) +8*a(n-3) -10*a(n-4) -21*a(n-5) +17*a(n-7) +12*a(n-8) -17*a(n-9) +2*a(n-10) +3*a(n-11) +3*a(n-12) -a(n-14) for n>15. %e A276249 Some solutions for n=4 %e A276249 ..0..1..1..2. .0..1..1..0. .0..0..1..2. .0..1..2..2. .0..1..2..0 %e A276249 ..2..2..0..1. .0..0..1..2. .2..2..1..0. .0..1..1..2. .2..0..1..1 %e A276249 ..1..2..0..0. .2..2..0..0. .0..2..1..0. .2..2..0..1. .1..2..0..0 %Y A276249 Cf. A276248. %K A276249 nonn %O A276249 1,1 %A A276249 _R. H. Hardin_, Aug 25 2016