%I #8 Jul 18 2017 08:02:18
%S 1,16,100,644,4188,27384,179612,1180228,7763498,51099608,336460302,
%T 2215852392,14594879684,96137054032,633284508204,4171739971970,
%U 27481572723178,181037861103928,1192612216360274,7856520861476702
%N Number of base 16 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.
%F G.f.: (1+6*x-41*x^2-22*x^3+83*x^4+6*x^5-39*x^6+x^7+4*x^8) / (1-10*x+19*x^2+30*x^3-45*x^4-14*x^5+21*x^6+x^7-2*x^8) (conjectured). - _Colin Barker_, Jul 18 2017
%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 16 differing by two or less A126403, one or less A126370.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 27 2006