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%I #5 Mar 31 2012 12:35:05
%S 1,26,124,600,2918,14236,69598,340774,1670480,8196280,40245610,
%T 197738510,972059180,4780678950,23520964308,115762376468,569912653284,
%U 2806482718416,13823453975028,68101963757630,335568968553598
%N Number of base 26 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 26 differing by one or less A126380.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006