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 A301952 #4 Mar 29 2018 12:46:46 %S A301952 0,5,20,123,680,4070,23565,138014,805249,4704141,27469522,160428571, %T A301952 936897912,5471539885,31953953498,186612354231,1089822896327, %U A301952 6364606387628,37169536347339,217071469820879,1267705419106309 %N A301952 Number of 3Xn 0..1 arrays with every element equal to 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301952 Row 3 of A301951. %H A301952 R. H. Hardin, <a href="/A301952/b301952.txt">Table of n, a(n) for n = 1..210</a> %F A301952 Empirical: a(n) = 4*a(n-1) +12*a(n-2) -5*a(n-3) -14*a(n-4) +14*a(n-6) +4*a(n-7) -3*a(n-8) -5*a(n-9) +a(n-10) for n>12 %e A301952 Some solutions for n=5 %e A301952 ..0..0..0..1..1. .0..0..0..0..0. .0..0..0..0..0. .0..0..0..1..0 %e A301952 ..0..1..0..1..1. .0..1..1..1..1. .1..1..1..0..0. .0..1..1..0..0 %e A301952 ..1..0..0..1..1. .1..0..0..1..1. .0..0..0..0..0. .0..0..1..1..1 %Y A301952 Cf. A301951. %K A301952 nonn %O A301952 1,2 %A A301952 _R. H. Hardin_, Mar 29 2018