%I #8 Jul 18 2017 08:01:08
%S 1,15,69,325,1543,7361,35223,168899,811105,3899407,18761375,90319881,
%T 434998065,2095690739,10098729091,48672013183,234609419433,
%U 1130969299775,5452365150693,26286944474683,126739125460983
%N Number of base 15 n-digit numbers with adjacent digits differing by two or less.
%C [Empirical] a(base,n)=a(base-1,n)+5^(n-1) for base>=2n-1; a(base,n)=a(base-1,n)+5^(n-1)-2 when base=2n-2.
%F G.f.: (1+6*x-46*x^2+14*x^3+102*x^4-25*x^5-52*x^6+5*x^7+2*x^8) / (1-9*x+20*x^2+10*x^3-46*x^4+x^5+23*x^6-x^7-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]`-$[i+1]`>2)+($[i+1]`-$[i]`>2))
%Y Cf. Base 15 differing by one or less A126369.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006