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 A281608 #4 Jan 25 2017 10:43:05 %S A281608 41,1617,12413,203276,3401430,52899445,839574485,13329701847, %T A281608 211084448862,3344465302550,52990220564149,839547337612225, %U A281608 13301641083138936,210748236247015012,3339047332719365760 %N A281608 Number of 5Xn 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 A281608 Row 5 of A281605. %H A281608 R. H. Hardin, <a href="/A281608/b281608.txt">Table of n, a(n) for n = 1..210</a> %e A281608 Some solutions for n=3 %e A281608 ..0..0..1. .0..1..2. .0..1..0. .0..1..2. .0..1..2. .0..1..1. .0..1..0 %e A281608 ..2..1..2. .1..2..0. .0..1..2. .1..2..0. .2..0..2. .0..2..0. .0..1..2 %e A281608 ..2..0..2. .0..2..1. .2..1..2. .1..2..1. .2..0..1. .0..2..0. .0..2..1 %e A281608 ..1..0..1. .0..1..0. .1..0..2. .0..2..0. .0..2..1. .1..2..1. .0..2..0 %e A281608 ..1..0..1. .0..2..2. .1..0..2. .0..1..1. .0..2..0. .1..0..1. .1..2..1 %Y A281608 Cf. A281605. %K A281608 nonn %O A281608 1,1 %A A281608 _R. H. Hardin_, Jan 25 2017