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 A281609 #4 Jan 25 2017 10:43:50 %S A281609 122,9188,95623,2563481,69506779,1732267694,44428349137,1138837839480, %T A281609 29102840547371,744335104686091,19034344218360000,486715748229292254, %U A281609 12445950255418792107,318255588377585182015,8138127052120466124265 %N A281609 Number of 6Xn 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 A281609 Row 6 of A281605. %H A281609 R. H. Hardin, <a href="/A281609/b281609.txt">Table of n, a(n) for n = 1..139</a> %e A281609 Some solutions for n=3 %e A281609 ..0..1..2. .0..1..0. .0..1..0. .0..0..1. .0..1..2. .0..1..0. .0..1..1 %e A281609 ..2..1..2. .2..2..0. .0..2..0. .2..2..1. .0..2..1. .0..2..1. .2..0..2 %e A281609 ..2..1..2. .1..0..1. .2..1..0. .0..0..1. .1..2..0. .1..0..1. .1..0..1 %e A281609 ..2..0..2. .1..0..2. .1..0..2. .1..2..2. .1..0..1. .1..0..1. .1..0..1 %e A281609 ..0..1..2. .2..0..1. .1..0..1. .0..1..0. .1..2..1. .2..0..2. .2..2..1 %e A281609 ..2..1..0. .1..0..1. .2..2..0. .2..1..0. .1..0..1. .1..1..2. .0..0..1 %Y A281609 Cf. A281605. %K A281609 nonn %O A281609 1,1 %A A281609 _R. H. Hardin_, Jan 25 2017