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%I #8 Jul 18 2017 08:02:09
%S 1,15,93,595,3845,24983,162805,1062635,6941843,45369865,296598577,
%T 1939229883,12680054343,82914396455,542185539797,3545445779213,
%U 23184429833549,151608454599649,991405196934357,6483050068051005
%N Number of base 15 n-digit numbers with adjacent digits differing by three or less.
%C [Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3.
%F G.f.: (1+6*x-31*x^2-40*x^3+48*x^4+35*x^5-19*x^6-5*x^7+2*x^8) / (1-9*x+11*x^2+37*x^3-20*x^4-29*x^5+8*x^6+4*x^7-x^8) (conjectured). - _Colin Barker_, Jul 18 2017
%o (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
%Y Cf. Base 15 differing by two or less A126402, one or less A126369.
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 27 2006
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