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 A298253 #6 May 03 2020 15:46:43 %S A298253 0,1,1,11,86,895,13991,435534,16014301,939457994 %N A298253 Number of n X n 0..1 arrays with every element equal to 2, 3, 5 or 8 king-move adjacent elements, with upper left element zero. %C A298253 Diagonal of A298259. %e A298253 Some solutions for n=7 %e A298253 ..0..0..0..0..1..0..0. .0..0..0..1..0..0..0. .0..0..0..1..1..0..0 %e A298253 ..0..1..1..0..1..1..0. .0..1..1..0..1..1..0. .0..1..1..0..1..0..1 %e A298253 ..1..1..0..1..1..1..1. .0..1..0..0..0..1..0. .1..0..1..0..0..1..1 %e A298253 ..1..0..1..0..1..0..0. .0..1..0..1..0..1..0. .1..0..1..0..1..0..1 %e A298253 ..1..0..1..0..1..1..0. .0..1..0..1..1..1..0. .1..1..0..1..1..0..1 %e A298253 ..0..1..1..0..0..1..0. .1..0..0..1..0..0..1. .1..0..1..1..0..0..1 %e A298253 ..0..0..0..1..1..0..0. .1..1..1..0..0..1..1. .0..0..1..1..0..1..1 %Y A298253 Cf. A298259. %K A298253 nonn %O A298253 1,4 %A A298253 _R. H. Hardin_, Jan 15 2018