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%I #8 Jul 18 2017 07:59:08
%S 1,15,43,125,365,1069,3137,9219,27123,79869,235361,693991,2047367,
%T 6042659,17841247,52694573,155679885,460055423,1359834747,4020216877,
%U 11887503933,35156155109,103985848697,307611659819,910083564731
%N Number of base 15 n-digit numbers with adjacent digits differing by one or less.
%C [Empirical] a(base,n)=a(base-1,n)+3^(n-1) for base>=n; a(base,n)=a(base-1,n)+3^(n-1)-2 when base=n-1.
%F G.f.: (1+7*x-57*x^2+73*x^3+75*x^4-121*x^5-33*x^6+37*x^7+4*x^8) / (1-8*x+20*x^2-8*x^3-30*x^4+24*x^5+12*x^6-8*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]`-$[i+1]`>1)+($[i+1]`-$[i]`>1))
%K nonn,base
%O 0,2
%A _R. H. Hardin_, Dec 26 2006
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