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%I #5 Mar 31 2012 12:35:06
%S 1,31,205,1379,9333,63399,431717,2944947,20115561,137543107,941258689,
%T 6445801999,44166431335,302771722951,2076414065529,14244985903467,
%U 97754711626643,671000257052461,4606822746884183,31634499742407797
%N Number of base 31 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 31 differing by two or less A126418, one or less A126385.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 27 2006