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 A221247 #6 Jul 23 2025 01:47:25 %S A221247 0,64,1056,45369,1337130,44315649,1404725868,45215769600, %T A221247 1447056039456,46405605611556,1487038748557464,47664362071029636, %U A221247 1527638149928473128,48962472488029102500,1569278944309473869112,50296658362620611720256 %N A221247 Number of 3Xn arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor. %C A221247 Row 3 of A221245 %H A221247 R. H. Hardin, <a href="/A221247/b221247.txt">Table of n, a(n) for n = 1..24</a> %e A221247 Some solutions for n=3 %e A221247 ..0..3..1....0..0..0....0..0..1....0..1..0....0..1..0....0..1..2....2..4..0 %e A221247 ..0..3..1....0..4..3....2..6..0....1..3..1....2..3..0....0..5..0....0..0..0 %e A221247 ..1..0..0....0..2..0....0..0..0....0..2..1....0..2..1....0..0..1....1..2..0 %K A221247 nonn %O A221247 1,2 %A A221247 _R. H. Hardin_ Jan 06 2013