%I #5 Mar 31 2012 12:35:06
%S 1,27,129,625,3043,14861,72723,356399,1748605,8586905,42198735,
%T 207504135,1020887305,5024819575,24741667433,121865892063,
%U 600430229661,2959070561939,14586392574071,71916648942815,354642311037069
%N Number of base 27 n-digit numbers with adjacent digits differing by two or less.
%C [Empirical] a(base,n)=a(base-1,n)+5^(n-1) for base>=2n-1; a(base,n)=a(base-1,n)+5^(n-1)-2 when base=2n-2
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>2)+($[i+1]`-$[i]`>2))
%Y Cf. Base 27 differing by one or less A126381.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006