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 A221127 #13 Mar 08 2025 02:31:11 %S A221127 1,144,4872,179300,6405243,229006550,8187649472,292733110656, %T A221127 10466092166432,374194374753326,13378578012147801,478324533007616827, %U A221127 17101545371715018992,611431849960750401963,21860533596256955469254,781580038958752812299025,27943844765222490485325201 %N A221127 Number of 3 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor. %H A221127 R. H. Hardin, <a href="/A221127/b221127.txt">Table of n, a(n) for n = 1..21</a> %e A221127 Some solutions for n=3: %e A221127 ..2..0..0....0..1..2....0..2..2....0..1..2....0..1..0....0..1..0....2..2..0 %e A221127 ..1..2..1....0..3..0....0..2..0....1..1..2....2..3..0....2..2..3....1..0..2 %e A221127 ..2..0..1....2..1..0....2..0..1....1..1..0....0..1..2....0..1..0....1..1..0 %Y A221127 Row 3 of A221125. %K A221127 nonn %O A221127 1,2 %A A221127 _R. H. Hardin_, Jan 02 2013