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 A221242 #6 Jul 23 2025 01:46:30 %S A221242 4,484,45369,4096576,367565584,32940435025,2951293792489, %T A221242 264404315544196,23687401278880161,2122092173450945536, %U A221242 190112409243526686921,17031641464052384231241,1525817148915719009233321 %N A221242 Number of nX4 arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor. %C A221242 Column 4 of A221245 %H A221242 R. H. Hardin, <a href="/A221242/b221242.txt">Table of n, a(n) for n = 1..21</a> %F A221242 Empirical: a(n) = 148*a(n-1) -6427*a(n-2) +118138*a(n-3) -1053200*a(n-4) +4793575*a(n-5) -11306353*a(n-6) +13398822*a(n-7) -7161939*a(n-8) +1435401*a(n-9) -59049*a(n-10) %e A221242 Some solutions for n=3 %e A221242 ..1..0..3..0....0..1..2..0....0..0..1..0....1..1..1..1....0..0..2..0 %e A221242 ..1..4..1..0....0..0..1..1....1..2..0..2....1..3..0..1....2..1..1..2 %e A221242 ..0..0..0..2....1..2..2..2....0..2..4..0....1..0..2..0....0..2..1..1 %K A221242 nonn %O A221242 1,1 %A A221242 _R. H. Hardin_ Jan 06 2013