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 A206686 #8 Jul 22 2025 19:36:18 %S A206686 1,4,44,916,31504,1915580,208563912,41832855136,15644344542416, %T A206686 10971573350181154 %N A206686 Number of n X n 0..3 arrays with no element equal to another within two positions in the same row or column, and new values 0..3 introduced in row major order. %C A206686 Diagonal of A206692 %e A206686 Some solutions for n=4 %e A206686 ..0..1..2..0....0..1..2..3....0..1..2..3....0..1..2..3....0..1..2..3 %e A206686 ..2..0..1..2....1..0..3..1....3..2..0..1....1..2..0..1....1..3..0..1 %e A206686 ..1..3..0..1....2..3..1..0....1..0..3..2....2..3..1..0....3..0..1..2 %e A206686 ..3..1..2..3....0..1..2..3....2..3..1..0....0..1..2..3....2..1..3..0 %K A206686 nonn %O A206686 1,2 %A A206686 _R. H. Hardin_ Feb 11 2012