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%I #7 Mar 31 2012 12:35:06
%S 1,19,151,1239,10271,85611,715649,5991499,50202083,420816645,
%T 3528266989,29585656541,248100670697,2080601208199,17448464481771,
%U 146328696766445,1227167540644629,10291514720245361,86308846158006385
%N Number of base 19 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 19 differing by three or less A126487, two or less A126406, one or less A126373.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006
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