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 A301956 #4 Mar 29 2018 12:49:32 %S A301956 0,233,5820,439078,21418808,1427656268,86143630040,5308792667591, %T A301956 324469928188515,19912146679826809,1220249427475855637, %U A301956 74810226305531953416,4585754748793488994754,281114995706301373466905 %N A301956 Number of 7Xn 0..1 arrays with every element equal to 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301956 Row 7 of A301951. %H A301956 R. H. Hardin, <a href="/A301956/b301956.txt">Table of n, a(n) for n = 1..210</a> %e A301956 Some solutions for n=5 %e A301956 ..0..0..0..0..0. .0..0..0..0..0. .0..0..0..0..0. .0..0..0..0..0 %e A301956 ..0..0..0..0..0. .0..0..0..0..0. .0..1..0..0..0. .0..0..0..0..0 %e A301956 ..1..1..1..0..0. .1..1..1..0..0. .1..0..1..0..0. .1..1..1..1..0 %e A301956 ..0..0..1..1..1. .1..1..0..0..0. .0..1..0..0..0. .0..0..0..0..0 %e A301956 ..1..1..0..0..1. .1..0..1..1..0. .1..1..1..1..1. .0..1..1..1..1 %e A301956 ..1..0..1..1..1. .0..0..0..0..0. .1..1..0..1..1. .1..0..1..0..1 %e A301956 ..0..0..0..0..0. .0..0..1..1..1. .1..0..1..1..1. .0..1..0..1..1 %Y A301956 Cf. A301951. %K A301956 nonn %O A301956 1,2 %A A301956 _R. H. Hardin_, Mar 29 2018