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 A301603 #4 Mar 24 2018 11:30:18 %S A301603 1,2,2,8,13,26,55,154,356,884,2161,5440,13511,33780,84398,211338, %T A301603 528999,1325014,3319005,8315948,20836784,52214530,130847203,327910100, %U A301603 821772985,2059471558,5161348174,12935209836,32417941793,81245379630,203616360639 %N A301603 Number of nX3 0..1 arrays with every element equal to 0, 2 or 3 horizontally or vertically adjacent elements, with upper left element zero. %C A301603 Column 3 of A301608. %H A301603 R. H. Hardin, <a href="/A301603/b301603.txt">Table of n, a(n) for n = 1..210</a> %F A301603 Empirical: a(n) = a(n-1) +3*a(n-2) +4*a(n-3) +2*a(n-4) -8*a(n-5) -17*a(n-6) -19*a(n-7) -9*a(n-8) +6*a(n-9) +21*a(n-10) +15*a(n-11) +11*a(n-12) -2*a(n-13) -2*a(n-14) -4*a(n-15) -a(n-16) -a(n-17) +a(n-18) %e A301603 Some solutions for n=5 %e A301603 ..0..0..0. .0..0..1. .0..0..0. .0..1..1. .0..1..1. .0..0..0. .0..0..0 %e A301603 ..0..0..0. .0..0..0. .0..1..0. .1..1..1. .1..1..1. .0..0..0. .0..1..0 %e A301603 ..0..1..0. .0..1..0. .0..0..0. .1..0..1. .1..0..1. .0..1..0. .0..0..0 %e A301603 ..0..0..0. .0..0..0. .0..1..0. .1..1..1. .1..1..1. .0..0..0. .1..1..1 %e A301603 ..0..0..0. .0..0..0. .0..0..0. .0..1..1. .1..1..0. .1..0..0. .1..1..1 %Y A301603 Cf. A301608. %K A301603 nonn %O A301603 1,2 %A A301603 _R. H. Hardin_, Mar 24 2018