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Number of base 19 n-digit numbers with adjacent digits differing by one or less.
4

%I #9 Jul 18 2017 12:25:42

%S 1,19,55,161,473,1393,4109,12135,35871,106113,314093,930187,2755955,

%T 8168423,24218539,71826449,213075513,632242305,1876395357,5569898331,

%U 16536545331,49103259773,145827049265,433134662087,1286649627671

%N Number of base 19 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+9*x-100*x^2+236*x^3-7*x^4-469*x^5+216*x^6+290*x^7-111*x^8-53*x^9+6*x^10) / ((1-2*x-x^2)*(1-8*x+20*x^2-8*x^3-31*x^4+28*x^5+10*x^6-12*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