Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #5 Dec 18 2015 18:18:25
%S 0,4,30,58081,78633756,4919350997521,720107530988047980,
%T 2283974100099963226425600
%N Number of n X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2
%C Diagonal of A221255
%e Some solutions for n=3
%e ..0..2..0....1..2..0....0..2..0....1..2..0....0..2..1....1..2..1....0..2..1
%e ..2..2..0....1..2..0....1..2..0....0..2..1....1..2..0....0..2..0....1..2..1
%e ..1..2..0....1..2..0....2..2..0....1..2..0....1..2..0....0..2..1....0..2..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 06 2013