A126513 - OEIS

%I #7 Mar 31 2012 12:35:06

%S 1,18,142,1158,9542,79050,656612,5461074,45448824,378357098,

%T 3150263772,26231558496,218432355062,1818936380306,15146831517282,

%U 126132762778328,1050352117472084,8746662279539970,72836658556602482

%N Number of base 18 n-digit numbers with adjacent digits differing by four or less.

%C [Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4

%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))

%Y Cf. Base 18 differing by three or less A126486, two or less A126405, one or less A126372.

%K nonn,base

%O 0,2

%A _R. H. Hardin_, Dec 28 2006