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 A202743 #9 Jul 22 2025 16:48:51 %S A202743 2,2,6,22,54,102,214,582,1590,3814,8662,20934,53942,137190,335574, %T A202743 815942,2032694,5139942,12902614,32059846,79807158,200325350, %U A202743 504502230,1267146054,3176193590,7975495910,20082938838,50611676614,127466481334 %N A202743 Number of 2Xn 0..1 arrays with row sums equal and column sums unequal to adjacent columns. %C A202743 Row 2 of A202742 %H A202743 R. H. Hardin, <a href="/A202743/b202743.txt">Table of n, a(n) for n = 1..168</a> %e A202743 Some solutions for n=5 %e A202743 ..1..1..0..1..0....0..1..0..1..1....1..0..1..1..0....0..1..1..1..0 %e A202743 ..0..1..0..1..1....1..1..0..0..1....1..0..0..1..1....0..1..0..1..1 %K A202743 nonn %O A202743 1,1 %A A202743 _R. H. Hardin_ Dec 23 2011