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 A301835 #7 Apr 20 2020 00:02:46 %S A301835 1,8,139,5748,496085,97439921,41966406867,39919204098331, %T A301835 84196647385137200,391960289300558475785,4034683591387591205214712, %U A301835 91832712356420807374009031299,4618825005074327343319160956639454 %N A301835 Number of n X n 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301835 Diagonal of A301841. %H A301835 R. H. Hardin, <a href="/A301835/b301835.txt">Table of n, a(n) for n = 1..16</a> %e A301835 Some solutions for n=5 %e A301835 ..0..0..0..1..0. .0..0..1..0..0. .0..0..1..0..0. .0..0..1..0..0 %e A301835 ..1..0..1..0..1. .0..1..0..1..0. .0..1..0..1..0. .0..0..0..1..0 %e A301835 ..1..0..1..0..0. .1..0..1..1..0. .1..0..0..1..0. .1..1..0..1..1 %e A301835 ..0..0..1..0..1. .1..0..0..1..1. .1..0..1..0..0. .1..1..0..1..0 %e A301835 ..0..0..1..0..0. .0..1..0..1..1. .0..0..1..0..1. .1..1..1..0..0 %Y A301835 Cf. A301841. %K A301835 nonn %O A301835 1,2 %A A301835 _R. H. Hardin_, Mar 27 2018