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 A280678 #4 Jan 07 2017 08:12:43 %S A280678 122,34096,2642832,287101721,29920114246,3130289979912, %T A280678 327452072560351,34253681605884733,3583141682779617309, %U A280678 374819732160862162533,39208546724956189523288,4101465758881532501508232 %N A280678 Number of 6Xn 0..2 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors and with new values introduced in order 0 sequentially upwards. %C A280678 Row 6 of A280673. %H A280678 R. H. Hardin, <a href="/A280678/b280678.txt">Table of n, a(n) for n = 1..133</a> %e A280678 Some solutions for n=2 %e A280678 ..0..1. .0..0. .0..1. .0..1. .0..1. .0..1. .0..0. .0..0. .0..1. .0..0 %e A280678 ..1..2. .1..2. .2..0. .2..0. .2..1. .0..2. .1..0. .1..2. .2..1. .1..0 %e A280678 ..1..2. .1..2. .1..1. .0..2. .0..2. .1..2. .1..0. .0..1. .0..0. .0..2 %e A280678 ..0..2. .2..0. .0..2. .1..2. .1..1. .2..0. .0..2. .0..2. .1..2. .1..2 %e A280678 ..0..0. .2..0. .1..0. .1..0. .2..0. .2..0. .1..0. .1..0. .2..1. .1..2 %e A280678 ..1..2. .1..1. .1..2. .2..0. .2..0. .1..0. .1..0. .1..0. .0..2. .1..2 %Y A280678 Cf. A280673. %K A280678 nonn %O A280678 1,1 %A A280678 _R. H. Hardin_, Jan 07 2017