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 A281198 #6 Apr 21 2020 13:01:37 %S A281198 0,2,56,270,1141,4248,14375,45614,138676,409976,1190740,3421202, %T A281198 9767347,27782656,78849645 %N A281198 Number of n X n 0..1 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. %C A281198 Diagonal of A281205. %e A281198 Some solutions for n=4 %e A281198 ..0..1..0..1. .0..1..0..1. .0..0..1..1. .0..1..1..0. .0..1..0..1 %e A281198 ..0..0..1..0. .1..1..0..0. .1..0..1..0. .0..0..1..0. .0..1..0..0 %e A281198 ..1..0..1..0. .0..1..1..0. .1..0..1..0. .1..0..1..1. .0..1..0..1 %e A281198 ..1..0..1..1. .0..0..1..0. .1..0..1..0. .0..1..0..0. .0..1..0..0 %Y A281198 Cf. A281205. %K A281198 nonn %O A281198 1,2 %A A281198 _R. H. Hardin_, Jan 17 2017