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 A280677 #4 Jan 07 2017 08:11:59 %S A280677 41,4568,181640,9439606,474736149,23952262535,1208240638772, %T A280677 60949510593245,3074564570571027,155095359625755139, %U A280677 7823728447342567501,394665220545896300250,19908746786901511218365,1004289676988490253656371 %N A280677 Number of 5Xn 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 A280677 Row 5 of A280673. %H A280677 R. H. Hardin, <a href="/A280677/b280677.txt">Table of n, a(n) for n = 1..210</a> %e A280677 Some solutions for n=3 %e A280677 ..0..1..0. .0..1..0. .0..1..0. .0..0..1. .0..1..0. .0..1..0. .0..1..0 %e A280677 ..0..2..1. .2..0..2. .2..0..1. .1..2..0. .2..0..2. .2..0..1. .0..2..1 %e A280677 ..1..2..2. .1..1..0. .2..2..1. .0..2..1. .1..0..1. .1..2..0. .0..0..1 %e A280677 ..1..1..2. .0..1..0. .1..2..2. .1..0..2. .0..1..0. .0..2..0. .2..1..2 %e A280677 ..2..1..1. .1..2..2. .1..0..1. .1..1..0. .0..1..0. .0..1..0. .2..1..2 %Y A280677 Cf. A280673. %K A280677 nonn %O A280677 1,1 %A A280677 _R. H. Hardin_, Jan 07 2017