%I #7 Mar 31 2012 12:35:01
%S 1,18,114,582,3466,20938,129642,813586,5161418,33012690,212531034,
%T 1375465890,8940439306,58322410658,381620168176,2503490173972,
%U 16459423126778,108417784128158,715300322712000,4725856346389840
%N Number of base 18 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