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 A267660 #6 Apr 20 2020 19:45:45 %S A267660 1,8,108,3143,80404,5663798,264709135,46354321490,3947286385526, %T A267660 1938755845909663 %N A267660 Number of n X n 0..1 arrays with every repeated value in every row unequal to the previous repeated value, and in every column equal to the previous repeated value, and new values introduced in row-major sequential order. %C A267660 Diagonal of A267667. %e A267660 Some solutions for n=5 %e A267660 ..0..0..1..0..1....0..0..1..0..1....0..1..0..1..1....0..0..1..1..0 %e A267660 ..0..1..0..0..1....1..0..1..0..1....1..1..0..0..1....1..1..0..0..1 %e A267660 ..0..1..0..1..1....0..0..1..0..1....0..0..1..0..1....1..0..1..1..0 %e A267660 ..1..0..1..0..0....1..0..1..0..1....0..1..0..0..1....1..0..1..0..1 %e A267660 ..0..1..0..1..1....1..0..0..1..1....0..1..0..1..1....0..1..0..0..1 %Y A267660 Cf. A267667. %K A267660 nonn %O A267660 1,2 %A A267660 _R. H. Hardin_, Jan 19 2016