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 A297500 #6 May 03 2020 15:31:30 %S A297500 1,10,110,2281,270845,66289769,28914051279,44145856928170, %T A297500 190314910908111935,1690602288933775004206,41411616264665765678770302 %N A297500 Number of n X n 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 or 2 neighboring 1's. %C A297500 Diagonal of A297506. %e A297500 Some solutions for n=4 %e A297500 ..0..0..1..1. .1..1..1..0. .0..1..1..1. .0..0..1..0. .0..0..1..1 %e A297500 ..0..0..0..0. .0..0..0..1. .0..0..0..0. .1..1..0..0. .0..0..1..0 %e A297500 ..1..1..0..0. .0..1..0..1. .1..1..1..0. .0..0..0..0. .1..0..0..1 %e A297500 ..1..0..0..0. .0..0..1..0. .0..0..0..1. .1..1..1..0. .0..1..1..0 %Y A297500 Cf. A297506. %K A297500 nonn %O A297500 1,2 %A A297500 _R. H. Hardin_, Dec 31 2017