%I #8 Mar 31 2012 12:35:02
%S 1,20,190,1490,13570,125970,1197064,11530924,112220506,1100369066,
%T 10850627100,107452404508,1067503597036,10630932961084,
%U 106062616838662,1059608800292250,10596747725262026,106055136504646382
%N Number of base 20 circular n-digit numbers with adjacent digits differing by 5 or less.
%C [Empirical] a(base,n)=a(base-1,n)+F(5) for base>=5.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]`-$[(i+1)mod N]`>5)+($[(i+1)mod N]`-$[i]`>5))
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006