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 A302260 #6 Jan 16 2024 09:34:00 %S A302260 4,29,153,818,4386,23516,126162,676988,3632880,19495940,104627364, %T A302260 561499304,3013389264,16171937024,86789899608,465775377536, %U A302260 2499677308656,13415022525008,71994427701360,386372643782240,2073546883713888 %N A302260 Number of n X 3 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302260 Column 3 of A302265. %H A302260 R. H. Hardin, <a href="/A302260/b302260.txt">Table of n, a(n) for n = 1..210</a> %F A302260 Empirical: a(n) = 6*a(n-1) -2*a(n-2) +2*a(n-3) -54*a(n-4) +16*a(n-5) for n>6. %e A302260 Some solutions for n=5 %e A302260 ..0..0..1. .0..0..1. .0..1..1. .0..1..0. .0..0..1. .0..1..0. .0..1..0 %e A302260 ..1..0..1. .0..0..1. .1..0..1. .0..1..0. .0..1..0. .1..1..1. .1..0..1 %e A302260 ..1..0..0. .1..1..0. .1..0..0. .1..0..1. .1..0..1. .0..1..1. .1..0..1 %e A302260 ..1..0..1. .1..1..0. .0..0..1. .1..1..0. .0..0..1. .0..1..0. .1..0..0 %e A302260 ..1..0..1. .0..0..1. .1..0..1. .0..1..0. .1..1..0. .1..0..1. .1..0..0 %Y A302260 Cf. A302265. %K A302260 nonn %O A302260 1,1 %A A302260 _R. H. Hardin_, Apr 04 2018