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 A296947 #8 Mar 02 2025 10:03:11 %S A296947 3,16,45,135,544,1765,5763,20811,70207,236330,822902,2806042,9547539, %T A296947 32855983,112351535,383730987,1315580367,4501742568,15396061261, %U A296947 52720880494,180431027632,617365998304,2113260768118,7232567686580 %N A296947 Number of n X 3 0..1 arrays with each 1 adjacent to 1, 3 or 5 king-move neighboring 1s. %C A296947 Column 3 of A296952. %H A296947 R. H. Hardin, <a href="/A296947/b296947.txt">Table of n, a(n) for n = 1..210</a> %F A296947 Empirical: a(n) = 3*a(n-1) +a(n-2) +16*a(n-3) -46*a(n-4) -20*a(n-5) -19*a(n-6) +148*a(n-7) +64*a(n-8) -58*a(n-9) -180*a(n-10) +9*a(n-11) +70*a(n-12) +35*a(n-13) -29*a(n-14) -13*a(n-15) +7*a(n-16) +6*a(n-17) +a(n-18) -2*a(n-19). %e A296947 Some solutions for n=7: %e A296947 ..0..0..0. .1..0..0. .1..1..1. .0..0..0. .0..1..1. .0..0..0. .0..0..0 %e A296947 ..1..1..0. .1..0..1. .1..1..1. .0..0..1. .0..1..1. .1..0..1. .1..1..1 %e A296947 ..0..0..0. .0..0..1. .0..0..0. .1..0..1. .0..0..0. .0..1..0. .1..1..1 %e A296947 ..0..0..1. .0..1..1. .1..1..0. .1..0..0. .0..1..1. .0..0..1. .0..0..0 %e A296947 ..0..0..1. .0..0..1. .0..0..0. .0..0..0. .0..1..1. .0..0..0. .0..0..0 %e A296947 ..1..0..0. .1..1..0. .1..0..1. .1..1..0. .0..1..1. .1..0..0. .1..0..0 %e A296947 ..0..1..0. .0..0..1. .1..0..1. .0..0..0. .0..0..0. .0..1..0. .1..0..0 %Y A296947 Cf. A296952. %K A296947 nonn %O A296947 1,1 %A A296947 _R. H. Hardin_, Dec 22 2017