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 A274722 #6 Apr 21 2020 12:38:31 %S A274722 1,6,68,1632,84948,8960464,1980677448,905233056800,860544738080372, %T A274722 1705630286322728068 %N A274722 Number of n X n 0..2 arrays with no element equal to any value at offset (-1,-2), (-2,-1) or (-1,0) and new values introduced in order 0..2. %C A274722 Diagonal of A274728. %e A274722 Some solutions for n=4 %e A274722 ..0..0..1..0. .0..1..0..1. .0..1..1..1. .0..1..0..1. .0..1..2..0 %e A274722 ..2..1..2..2. .1..0..1..2. .1..0..2..0. .2..0..2..2. .1..0..1..2 %e A274722 ..1..2..1..0. .0..2..0..1. .2..1..0..2. .1..1..0..1. .2..1..0..1 %e A274722 ..0..0..0..1. .2..0..2..0. .0..0..1..0. .0..0..2..0. .1..0..1..2 %Y A274722 Cf. A274728. %K A274722 nonn %O A274722 1,2 %A A274722 _R. H. Hardin_, Jul 03 2016