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%I #13 Jul 18 2017 01:46:01
%S 1,11,79,591,4441,33391,251077,1887941,14196143,106746189,802665137,
%T 6035544031,45383547985,341256134861,2566034493807,19294987989285,
%U 145086343307233,1090959321972847,8203337509713921,61684010524412861
%N Number of base 11 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.
%F G.f.: (1-x-x^2)*(1+4*x-2*x^2-4*x^3+2*x^4) / ((1-x)*(1-7*x-5*x^2+8*x^3+2*x^4-2*x^5)) (conjectured). - _Colin Barker_, Jul 17 2017
%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 11 differing by three or less A126479, two or less A126398, one or less A126365.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 28 2006
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