A126515 - OEIS

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

%S 1,20,160,1320,11000,92172,774696,6522504,54969166,463511924,

%T 3909629218,32982588380,278275931230,2347955939840,19811499262410,

%U 167167589771462,1410557938634156,11902332555068524,100432557218234836

%N Number of base 20 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 20 differing by three or less A126488, two or less A126407, one or less A126374.

%K nonn,base

%O 0,2

%A _R. H. Hardin_, Dec 28 2006