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%I #5 Mar 31 2012 12:35:06
%S 1,28,134,650,3168,15486,75848,372024,1826730,8977530,44151860,
%T 217269760,1069715430,5268960200,25962370558,127969407686,
%U 630947807506,3111658441818,15349331786976,75731342285276,373715745367376
%N Number of base 28 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 28 differing by one or less A126382.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006