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 A202744 #9 Jul 22 2025 16:48:58 %S A202744 2,8,38,140,638,3032,14258,70136,350594,1767452,9029918,46519544, %T A202744 241210598,1258499756,6598909298,34748813672,183679125026, %U A202744 974136322892,5181534476414,27634187724392,147730324961126,791463055043228 %N A202744 Number of 3Xn 0..1 arrays with row sums equal and column sums unequal to adjacent columns. %C A202744 Row 3 of A202742 %H A202744 R. H. Hardin, <a href="/A202744/b202744.txt">Table of n, a(n) for n = 1..50</a> %e A202744 Some solutions for n=5 %e A202744 ..1..0..1..0..0....1..1..0..0..0....1..1..0..1..0....0..1..0..1..1 %e A202744 ..1..0..0..0..1....0..1..0..1..0....1..1..0..1..0....1..1..0..1..0 %e A202744 ..0..1..1..0..0....0..0..1..1..0....1..0..0..1..1....1..1..0..1..0 %K A202744 nonn %O A202744 1,1 %A A202744 _R. H. Hardin_ Dec 23 2011