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 A293090 #6 Apr 05 2020 23:42:16 %S A293090 0,10,498,8108,125848,1900201,28709764,435581165,6638075636, %T A293090 101571134541,1559620441607,24020341461662,370919586815724, %U A293090 5740889185248758,89034754024149656,1383318002074531596,21526968518644809557 %N A293090 Number of 4 X n 0..1 arrays with the number of 1's horizontally or antidiagonally adjacent to some 0 two less than the number of 0's adjacent to some 1. %C A293090 Row 4 of A293087. %H A293090 R. H. Hardin, <a href="/A293090/b293090.txt">Table of n, a(n) for n = 1..174</a> %e A293090 Some solutions for n=4 %e A293090 ..1..0..0..0. .0..0..1..1. .1..1..0..1. .1..1..0..0. .0..0..0..1 %e A293090 ..0..1..0..0. .0..1..1..0. .0..0..1..0. .0..0..0..0. .1..0..0..0 %e A293090 ..1..1..1..1. .0..0..0..0. .0..1..1..0. .1..0..1..0. .1..0..0..1 %e A293090 ..0..0..1..1. .0..0..0..0. .0..1..0..0. .1..1..1..0. .0..0..0..1 %Y A293090 Cf. A293087. %K A293090 nonn %O A293090 1,2 %A A293090 _R. H. Hardin_, Sep 30 2017