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 A302878 #4 Apr 15 2018 10:35:06 %S A302878 4,6,17,35,72,241,722,1821,4863,14841,43444,119306,335624,985356, %T A302878 2849009,8044468,22928355,66336411,190801483,543986757,1556622000, %U A302878 4478561650,12855871827,36783013974,105393294206,302583744944,867943015259 %N A302878 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 3, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302878 Row 3 of A302877. %H A302878 R. H. Hardin, <a href="/A302878/b302878.txt">Table of n, a(n) for n = 1..210</a> %F A302878 Empirical: a(n) = a(n-1) +3*a(n-2) +2*a(n-3) +36*a(n-4) -22*a(n-5) -100*a(n-6) -5*a(n-7) -280*a(n-8) +97*a(n-9) +725*a(n-10) -111*a(n-11) +481*a(n-12) -72*a(n-13) -1160*a(n-14) +511*a(n-15) +19*a(n-16) +9*a(n-17) +24*a(n-18) -10*a(n-19) -a(n-20) for n>21 %e A302878 Some solutions for n=5 %e A302878 ..0..1..1..1..0. .0..1..0..0..0. .0..1..0..1..0. .0..1..0..1..1 %e A302878 ..0..1..0..1..0. .1..1..0..1..0. .0..1..0..1..0. .0..1..0..0..0 %e A302878 ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..0..0. .0..1..1..1..0 %Y A302878 Cf. A302877. %K A302878 nonn %O A302878 1,1 %A A302878 _R. H. Hardin_, Apr 15 2018