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 A289650 #6 Apr 05 2020 23:35:23 %S A289650 3,2421,183390,25760875,2439241607,332113863074,35072966294346, %T A289650 4615203834449304,519140871714574338,66784349259505575111, %U A289650 7809000921229551589905,991318340748862385457430 %N A289650 Number of n X 7 0..1 arrays with the number of 1's horizontally, antidiagonally or vertically adjacent to some 0 two less than the number of 0's adjacent to some 1. %C A289650 Column 7 of A289651. %H A289650 R. H. Hardin, <a href="/A289650/b289650.txt">Table of n, a(n) for n = 1..31</a> %e A289650 Some solutions for n=3 %e A289650 ..0..0..0..0..0..1..0. .0..0..0..1..0..1..1. .0..1..0..0..0..0..1 %e A289650 ..0..1..1..0..1..0..0. .1..0..1..1..0..0..0. .1..0..0..0..0..1..1 %e A289650 ..0..1..1..1..1..0..1. .1..1..0..0..0..0..1. .0..0..0..0..0..1..1 %Y A289650 Cf. A289651. %K A289650 nonn %O A289650 1,1 %A A289650 _R. H. Hardin_, Jul 09 2017