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%I #5 Mar 31 2012 12:35:05
%S 1,20,94,450,2168,10486,50848,247024,1201730,5852530,28526860,
%T 139144760,679090456,3315836420,16196773236,79141717426,386812618952,
%U 1891013450430,9246370600422,45218609940844,221167392509842
%N Number of base 20 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 20 differing by one or less A126374.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006
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