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 A281606 #4 Jan 25 2017 10:41:35 %S A281606 5,50,209,1283,8180,49572,302304,1849212,11295326,69003066,421598546, %T A281606 2575763454,15736620000,96143466614,587391366384,3588683849428, %U A281606 21925168436114,133952450888038,818386359248384,4999955088202190 %N A281606 Number of 3Xn 0..2 arrays with no element equal to more than one of its horizontal, diagonal or antidiagonal neighbors and with new values introduced in order 0 sequentially upwards. %C A281606 Row 3 of A281605. %H A281606 R. H. Hardin, <a href="/A281606/b281606.txt">Table of n, a(n) for n = 1..210</a> %F A281606 Empirical: a(n) = 6*a(n-1) -4*a(n-2) +29*a(n-3) -15*a(n-4) +73*a(n-5) +11*a(n-6) -32*a(n-7) +6*a(n-8) +a(n-9) -30*a(n-10) -26*a(n-11) +10*a(n-12) +8*a(n-13) for n>15 %e A281606 Some solutions for n=4 %e A281606 ..0..1..0..1. .0..1..0..1. .0..1..0..2. .0..1..2..1. .0..1..1..0 %e A281606 ..2..1..2..1. .0..1..2..1. .0..2..0..2. .1..2..0..1. .2..0..2..2 %e A281606 ..2..0..2..0. .2..1..0..0. .1..2..0..1. .0..2..0..2. .2..1..1..0 %Y A281606 Cf. A281605. %K A281606 nonn %O A281606 1,1 %A A281606 _R. H. Hardin_, Jan 25 2017