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 A280358 #7 Dec 31 2023 16:15:24 %S A280358 4,50,571,6727,78800,924579,10844773,127214104,1492251709,17504551617, %T A280358 205333329586,2408618523801,28253780677867,331424891961162, %U A280358 3887708335839063,45603925604339175,534947030615649624 %N A280358 Number of n X 3 0..2 arrays with no element equal to more than one of its horizontal and vertical neighbors and with new values introduced in order 0 sequentially upwards. %C A280358 Column 3 of A280362. %H A280358 R. H. Hardin, <a href="/A280358/b280358.txt">Table of n, a(n) for n = 1..210</a> %F A280358 Empirical: a(n) = 10*a(n-1) +26*a(n-2) -58*a(n-3) -99*a(n-4) -63*a(n-5) -25*a(n-6) +229*a(n-7) -3*a(n-8) -16*a(n-9) +12*a(n-10) +16*a(n-12). %e A280358 Some solutions for n=4 %e A280358 ..0..1..1. .0..0..1. .0..1..0. .0..1..2. .0..1..2. .0..0..1. .0..1..2 %e A280358 ..2..0..2. .2..2..0. .1..2..1. .2..0..1. .2..0..2. .2..2..0. .1..2..1 %e A280358 ..1..0..2. .0..1..1. .1..0..0. .2..1..2. .0..1..0. .0..0..2. .0..2..0 %e A280358 ..0..2..0. .2..0..0. .0..1..2. .1..0..1. .1..2..1. .1..1..0. .0..1..0 %Y A280358 Cf. A280362. %K A280358 nonn %O A280358 1,1 %A A280358 _R. H. Hardin_, Jan 01 2017