%I
%S 1,4,162,75398,386994338,22039625597766,13914188992963436802,
%T 97391265572623379728784646,7557580190940015054807296049439074,
%U 6502004785230840000033839573162175747164038
%N Number of n X n arrays with entries in 1..4 in which adjacent entries differ by 2 or less (adjacent means in x or y directions).
%C [Empirical] a(base+1,n,diff)=a(base,n,diff)+F(n,diff) for base>=2.diff.(n1) and F(n,diff)= (n=2, A063496(diff+1)) (n=3, A068744(diff+1)) (n=4, A068745(diff+1)) (n=5, A068746(diff+1)) (n=6, A068747(diff+1))
%o (S/R) stvar $[N][N]:(0.. M1) init $[][]:=0 asgn $[][]>{*} kill +[i in 0.. N2](+[j in 0.. N1](($[i][j]`$[i+1][j]`>2)+($[i+1][j]`$[i][j]`>2)+($[j][i]`$[j][i+1]`>2)+($[j][i+1]`$[j][i]`>2)))
%K nonn
%O 0,2
%A _R. H. Hardin_, Dec 31 2006
