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 A301668 #4 Mar 25 2018 11:37:38 %S A301668 8,421,5289,71564,1073621,15498505,225780260,3307561389,48158543096, %T A301668 703127937300,10259186324647,149696614458243,2184338617470806, %U A301668 31873058777880129,465081902561442941,6786326832276152384 %N A301668 Number of nX7 0..1 arrays with every element equal to 1, 2 or 4 horizontally or vertically adjacent elements, with upper left element zero. %C A301668 Column 7 of A301669. %H A301668 R. H. Hardin, <a href="/A301668/b301668.txt">Table of n, a(n) for n = 1..210</a> %e A301668 Some solutions for n=5 %e A301668 ..0..0..0..1..1..0..0. .0..0..1..1..0..0..1. .0..0..0..1..1..0..1 %e A301668 ..0..1..1..0..0..1..1. .0..1..0..0..1..0..1. .0..1..0..0..1..0..1 %e A301668 ..0..0..1..0..1..0..1. .0..1..0..1..1..0..1. .0..1..1..0..1..1..0 %e A301668 ..1..0..1..0..1..0..1. .0..1..0..1..0..0..0. .0..0..0..1..0..1..0 %e A301668 ..1..1..0..0..1..0..1. .0..1..0..1..1..0..0. .1..1..0..1..0..1..1 %Y A301668 Cf. A301669. %K A301668 nonn %O A301668 1,1 %A A301668 _R. H. Hardin_, Mar 25 2018