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 A282990 #9 Oct 20 2023 15:06:48 %S A282990 4,11,33,98,291,865,2570,7637,22693,67432,200373,595405,1769236, %T A282990 5257255,15621845,46420050,137936399,409875693,1217938738,3619084505, %U A282990 10754048825,31955475472,94955158681,282157659273,838426745764,2491370993875 %N A282990 Number of nX2 0..1 arrays with no 1 equal to more than one of its horizontal and vertical neighbors. %C A282990 Column 2 of A282996, A295275. %H A282990 R. H. Hardin, <a href="/A282990/b282990.txt">Table of n, a(n) for n = 1..210</a> %F A282990 Empirical: a(n) = 2*a(n-1) +3*a(n-2) -a(n-4). %F A282990 Empirical: G.f.: -x*(-4-3*x+x^2+x^3)/(1-2*x-3*x^2+x^4) . - _R. J. Mathar_, Mar 02 2017 %e A282990 Some solutions for n=5 %e A282990 ..0..0. .1..1. .1..0. .0..0. .1..1. .1..0. .0..1. .1..0. .1..0. .0..0 %e A282990 ..0..1. .0..0. .1..0. .1..0. .0..0. .0..0. .1..0. .1..0. .0..0. .0..1 %e A282990 ..1..0. .0..0. .0..1. .0..0. .0..0. .0..1. .0..0. .0..0. .0..0. .0..0 %e A282990 ..0..1. .0..0. .1..0. .1..0. .0..0. .0..0. .0..0. .0..0. .0..1. .0..0 %e A282990 ..0..0. .0..0. .0..0. .1..0. .1..1. .0..1. .0..0. .1..1. .1..0. .1..1 %Y A282990 Cf. A282996, A295275. %K A282990 nonn %O A282990 1,1 %A A282990 _R. H. Hardin_, Feb 26 2017