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A126374
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Number of base 20 n-digit numbers with adjacent digits differing by one or less.
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4
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1, 20, 58, 170, 500, 1474, 4352, 12864, 38058, 112674, 333776, 989236, 2933102, 8699864, 25812862, 76609418, 227424420, 675289026, 2005535520, 5957318820, 17698806798, 52590044172, 156287402420, 464515721050, 1380792800096
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OFFSET
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0,2
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COMMENTS
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[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.
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LINKS
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FORMULA
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G.f.: (1+9*x-117*x^2+356*x^3-266*x^4-399*x^5+546*x^6+82*x^7-216*x^8+x^9+12*x^10) / ((1-2*x)*(1-4*x+3*x^2+x^3)*(1-5*x+4*x^2+8*x^3-5*x^4-3*x^5+x^6)) (conjectured). - Colin Barker, Jul 18 2017
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PROG
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(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>1)+($[i+1]`-$[i]`>1))
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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