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 #8 May 19 2023 15:27:56
%S 1,1,114,11734,86954982,329877369234
%N Number of n X n 0..3 arrays with values 0..3 introduced in row major order, the number of instances of each value within one of each other, and every element equal to zero or two horizontal or vertical neighbors.
%C Diagonal of A199201.
%e Some solutions for n=4
%e ..0..1..2..1....0..1..0..2....0..1..0..2....0..1..0..1....0..1..2..0
%e ..3..2..0..2....2..3..2..0....2..0..3..1....1..2..3..0....3..2..1..3
%e ..0..1..3..0....3..1..3..1....3..1..2..0....2..3..0..3....0..1..3..1
%e ..2..3..1..3....2..0..1..3....2..3..1..3....3..2..1..2....2..0..2..3
%Y Cf. A199201.
%K nonn
%O 1,3
%A _R. H. Hardin_, Nov 03 2011