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 A300210 #6 Jun 26 2025 10:26:52 %S A300210 4,32,228,1651,11965,86775,629440,4566023,33122989,240283124, %T A300210 1743081647,12644813016,91729105941,665429316237,4827215711786, %U A300210 35018011778092,254030734032018,1842812043966813,13368288852038965,96977414177346279 %N A300210 Number of n X 3 0..1 arrays with every element equal to 0, 1, 2, 3, 4, 5, 7 or 8 king-move adjacent elements, with upper left element zero. %C A300210 Column 3 of A300215. %H A300210 R. H. Hardin, <a href="/A300210/b300210.txt">Table of n, a(n) for n = 1..210</a> %F A300210 Empirical: a(n) = 8*a(n-1) -4*a(n-2) -8*a(n-3) -15*a(n-4) -4*a(n-5) -25*a(n-6) -44*a(n-7) -12*a(n-8). %e A300210 Some solutions for n=5 %e A300210 ..0..1..0. .0..0..0. .0..1..1. .0..0..1. .0..0..1. .0..0..0. .0..0..1 %e A300210 ..0..1..0. .0..0..1. .0..0..0. .0..1..0. .0..1..1. .1..1..1. .0..0..1 %e A300210 ..1..0..1. .0..1..1. .0..1..1. .0..1..0. .0..1..0. .1..1..0. .0..0..1 %e A300210 ..1..1..0. .1..0..1. .0..1..0. .1..1..0. .1..0..1. .1..0..0. .0..0..1 %e A300210 ..0..0..1. .0..0..1. .1..1..1. .0..1..1. .1..0..0. .0..1..1. .0..0..1 %Y A300210 Cf. A300215. %K A300210 nonn %O A300210 1,1 %A A300210 _R. H. Hardin_, Feb 28 2018