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 A302809 #4 Apr 13 2018 13:09:58 %S A302809 4,32,169,934,5117,28128,154494,848519,4660562,25597855,140595667, %T A302809 772217905,4241385457,23295695745,127950975583,702767266506, %U A302809 3859930159709,21200561758854,116443510741144,639562826045595 %N A302809 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 2, 3 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302809 Row 3 of A302808. %H A302809 R. H. Hardin, <a href="/A302809/b302809.txt">Table of n, a(n) for n = 1..210</a> %F A302809 Empirical: a(n) = 3*a(n-1) +14*a(n-2) +2*a(n-3) -22*a(n-4) +3*a(n-5) +37*a(n-6) -19*a(n-7) -4*a(n-8) +24*a(n-9) -4*a(n-10) +11*a(n-11) +8*a(n-12) +2*a(n-13) for n>15 %e A302809 Some solutions for n=5 %e A302809 ..0..0..1..0..0. .0..1..0..1..0. .0..1..1..0..0. .0..0..0..1..1 %e A302809 ..0..1..0..1..0. .1..1..1..0..0. .1..0..1..1..1. .0..0..1..0..0 %e A302809 ..1..0..0..1..0. .0..0..1..0..1. .0..1..0..0..0. .1..1..1..1..1 %Y A302809 Cf. A302808. %K A302809 nonn %O A302809 1,1 %A A302809 _R. H. Hardin_, Apr 13 2018