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%I #7 Mar 31 2012 12:35:06
%S 1,27,223,1887,16103,138099,1188039,10242351,88435341,764407997,
%T 6612526647,57234605067,495599614141,4292742043159,37190688714579,
%U 322257543592553,2792687844075253,24203507849388273,209778422093025849
%N Number of base 27 n-digit numbers with adjacent digits differing by four or less.
%C [Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))
%Y Cf. Base 27 differing by three or less A126495, two or less A126414, one or less A126381.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006
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