%I #8 Mar 31 2012 12:35:02

%S 1,16,166,1486,15202,158846,1690522,18157862,196069282,2123310106,

%T 23030866946,250026499442,2715618543442,29502879144794,

%U 320569057857074,3483472289498786,37854839472704386,411377395552788114

%N Number of base 16 circular n-digit numbers with adjacent digits differing by 6 or less.

%C [Empirical] a(base,n)=a(base-1,n)+F(6) for base>=6.int(n/2)+1 and F(d) is the largest coefficient in (1+x+...+x^(2d))^n

%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>6)+($[(i+1)mod N]`-$[i]`>6))

%K nonn,base

%O 0,2

%A _R. H. Hardin_, Dec 28 2006