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%I #5 Mar 31 2012 12:35:06
%S 1,26,170,1134,7618,51394,347682,2356702,15997846,108719102,739490656,
%T 5033426494,34279838804,233566488998,1591993821168,10854281793638,
%U 74022763799812,504910336091974,3444546058508588,23502038289723148
%N Number of base 26 n-digit numbers with adjacent digits differing by three or less.
%C [Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
%Y Cf. Base 26 differing by two or less A126413, one or less A126380.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 27 2006
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