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 A268996 #7 Jan 18 2019 06:33:02 %S A268996 4,13,35,103,278,763,2037,5421,14264,37321,97015,250963,646250, %T A268996 1657719,4237481,10798553,27442092,69563653,175938699,444060607, %U A268996 1118668286,2813233523,7063416349,17708464645,44335423456,110857865665,276863340767 %N A268996 Number of 2 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once. %H A268996 R. H. Hardin, <a href="/A268996/b268996.txt">Table of n, a(n) for n = 1..210</a> %F A268996 Empirical: a(n) = 2*a(n-1) + 5*a(n-2) - 4*a(n-3) - 11*a(n-4) - 6*a(n-5) - a(n-6). %F A268996 Empirical g.f.: x*(4 + 5*x - 11*x^2 - 16*x^3 - 7*x^4 - x^5) / ((1 + x)^2*(1 - 2*x - x^2)^2). - _Colin Barker_, Jan 18 2019 %e A268996 Some solutions for n=4: %e A268996 ..1..0..0..0. .1..0..0..0. .1..1..0..0. .1..0..0..0. .1..0..1..0 %e A268996 ..0..0..1..1. .1..0..0..1. .0..0..0..1. .1..0..1..1. .0..0..0..1 %Y A268996 Row 2 of A268995. %K A268996 nonn %O A268996 1,1 %A A268996 _R. H. Hardin_, Feb 17 2016