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 A276294 #8 Feb 05 2019 18:42:28 %S A276294 2,12,45,189,805,3437,14693,62829,268677,1148973,4913509,21012333, %T A276294 89858053,384272941,1643321829,7027574381,30053031045,128520116269, %U A276294 549609131621,2350372894061,10051239005445,42983564779053 %N A276294 Number of n X 3 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,1) or (0,-1) and new values introduced in order 0..2. %H A276294 R. H. Hardin, <a href="/A276294/b276294.txt">Table of n, a(n) for n = 1..210</a> %F A276294 Empirical: a(n) = 6*a(n-1) - 8*a(n-2) + 4*a(n-3) - 7*a(n-4) + 6*a(n-5) for n>7. %F A276294 Empirical g.f.: x*(2 - 11*x^2 + 7*x^3 - 3*x^4 + 11*x^5 - 2*x^6) / ((1 - x)*(1 - 5*x + 3*x^2 - x^3 + 6*x^4)). - _Colin Barker_, Feb 05 2019 %e A276294 Some solutions for n=4: %e A276294 ..0..1..2. .0..1..2. .0..1..2. .0..1..2. .0..1..0. .0..1..0. .0..1..2 %e A276294 ..2..1..2. .2..1..2. .2..1..0. .0..1..2. .2..1..0. .2..1..2. .0..1..2 %e A276294 ..2..1..2. .0..1..2. .0..1..2. .0..1..0. .0..1..0. .2..1..2. .2..1..0 %e A276294 ..0..1..2. .2..0..2. .2..0..2. .0..1..2. .0..1..0. .2..1..0. .0..2..0 %Y A276294 Column 3 of A276299. %K A276294 nonn %O A276294 1,1 %A A276294 _R. H. Hardin_, Aug 28 2016