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 A301540 #4 Mar 23 2018 11:06:36 %S A301540 21,86,374,1841,9037,47791,255406,1432328,8145489,46701775,269741883, %T A301540 1568279203,9153838956,53577605791,314145731065,1844204380914, %U A301540 10835966335712,63710021424647,374740321237045,2204822119962792 %N A301540 Number of nX7 0..1 arrays with every element equal to 0, 1 or 3 horizontally or vertically adjacent elements, with upper left element zero. %C A301540 Column 7 of A301541. %H A301540 R. H. Hardin, <a href="/A301540/b301540.txt">Table of n, a(n) for n = 1..156</a> %e A301540 Some solutions for n=5 %e A301540 ..0..0..0..1..0..1..1. .0..0..0..1..1..1..0. .0..1..0..0..0..1..0 %e A301540 ..1..0..1..0..0..0..0. .1..0..1..0..1..0..1. .1..0..1..0..1..0..0 %e A301540 ..1..1..0..1..1..0..1. .0..1..0..0..0..1..0. .0..1..0..1..0..1..0 %e A301540 ..1..0..0..0..0..1..0. .1..0..1..1..1..0..1. .1..0..1..0..1..0..1 %e A301540 ..0..1..1..0..1..0..1. .0..0..0..1..0..0..0. .0..1..0..1..0..1..0 %Y A301540 Cf. A301541. %K A301540 nonn %O A301540 1,1 %A A301540 _R. H. Hardin_, Mar 23 2018