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 A295913 #10 May 02 2023 15:24:56 %S A295913 5,13,39,115,337,993,2919,8587,25257,74289,218511,642715,1890449, %T A295913 5560465,16355255,48106475,141497817,416194129,1224171199,3600711835, %U A295913 10590941633,31151630513,91627743527,269508954923,792719257161,2331662118065 %N A295913 Number of n X 3 0..1 arrays with each 1 adjacent to 0 or 3 king-move neighboring 1's. %H A295913 R. H. Hardin, <a href="/A295913/b295913.txt">Table of n, a(n) for n = 1..210</a> %F A295913 Empirical: a(n) = 2*a(n-1) + 3*a(n-2) - 2*a(n-4). %F A295913 Empirical g.f.: x*(5 + 3*x - 2*x^2 - 2*x^3) / (1 - 2*x - 3*x^2 + 2*x^4). - _Colin Barker_, Feb 22 2019 %e A295913 Some solutions for n=7: %e A295913 ..0..0..1. .1..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..1..1 %e A295913 ..0..0..0. .0..0..0. .0..1..1. .0..0..0. .0..0..0. .1..0..1. .0..1..1 %e A295913 ..0..1..0. .0..0..0. .0..1..1. .1..0..1. .0..1..1. .0..0..0. .0..0..0 %e A295913 ..0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..1..1. .0..0..0. .1..0..1 %e A295913 ..0..0..0. .1..1..0. .0..0..0. .0..0..0. .0..0..0. .1..0..0. .0..0..0 %e A295913 ..0..0..0. .1..1..0. .0..0..0. .1..0..0. .1..0..0. .0..0..0. .0..0..0 %e A295913 ..1..0..0. .0..0..0. .0..0..1. .0..0..1. .0..0..1. .0..0..1. .0..0..0 %Y A295913 Column 3 of A295918. %K A295913 nonn %O A295913 1,1 %A A295913 _R. H. Hardin_, Nov 29 2017