%I #7 Mar 31 2012 12:35:01
%S 1,20,128,656,3928,23840,148304,934968,5958552,38285216,247607348,
%T 1609914524,10513615792,68913452056,453123210178,2987405569166,
%U 19741419610536,130718419293680,867078544410362,5760352822741182
%N Number of base 20 circular n-digit numbers with adjacent digits differing by 3 or less.
%C [Empirical] a(base,n)=a(base-1,n)+A025012(n+1) for base>=3.int(n/2)+1
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>3)+($[(i+1)mod N]`-$[i]`>3))
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006