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 A301791 #9 Apr 03 2018 04:16:39 %S A301791 2,5,6,9,14,22,35,56,90,145,234,378,611,988,1598,2585,4182,6766,10947, %T A301791 17712,28658,46369,75026,121394,196419,317812,514230,832041,1346270, %U A301791 2178310,3524579,5702888,9227466,14930353,24157818,39088170,63245987 %N A301791 Number of 2Xn 0..1 arrays with every element equal to 0 or 1 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301791 Row 2 of A301790. %H A301791 R. H. Hardin, <a href="/A301791/b301791.txt">Table of n, a(n) for n = 1..210</a> %F A301791 Empirical: a(n) = 2*a(n-1) -a(n-3) for n>5. %e A301791 Some solutions for n=5 %e A301791 ..0..0..1..0..0. .0..1..0..0..1. .0..1..0..1..1. .0..1..0..0..1 %e A301791 ..1..0..1..1..0. .0..1..1..0..0. .0..1..0..0..1. .0..1..1..0..1 %Y A301791 Cf. A301790, A020706, A048577. %K A301791 nonn %O A301791 1,1 %A A301791 _R. H. Hardin_, Mar 26 2018