A126521 - OEIS

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

%S 1,26,214,1806,15374,131538,1128990,9710910,83652388,721363974,

%T 6225222156,53750847042,464278918952,4011329573242,34664086928592,

%U 299591386800116,2589524785835700,22384118655449566,193499832018326518

%N Number of base 26 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 26 differing by three or less A126494, two or less A126413, one or less A126380.

%K nonn,base

%O 0,2

%A _R. H. Hardin_, Dec 28 2006