%I #11 Feb 22 2025 14:34:10
%S 1,15,16714,1084539825,1814002928583853,72341858272434900016248
%N Number of n X n 0..4 arrays with values 0..4 introduced in row major order and each element equal to no more than two horizontal and vertical neighbors.
%e Some solutions for n=4:
%e ..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0
%e ..0..1..1..2....0..1..1..1....0..1..1..0....0..1..1..1....0..1..1..2
%e ..2..1..3..0....2..1..3..4....2..1..3..0....2..1..0..2....3..0..0..3
%e ..1..2..1..0....1..3..4..0....3..0..0..0....2..0..0..2....3..4..0..1
%Y Diagonal of A198528.
%K nonn,more,changed
%O 1,2
%A _R. H. Hardin_, Oct 26 2011