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A126488
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Number of base 20 n-digit numbers with adjacent digits differing by three or less.
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2
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1, 20, 128, 840, 5560, 36988, 246840, 1650808, 11056590, 74130748, 497387482, 3339002940, 22423219250, 150623072388, 1011962290858, 6799752144942, 45694220498130, 307084056184964, 2063824981953422, 13870824556736138
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listen;
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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)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3.
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LINKS
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FORMULA
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G.f.: (1+9*x-69*x^2-55*x^3+242*x^4+192*x^5-94*x^6-73*x^7+5*x^8+4*x^9) / (1-11*x+23*x^2+53*x^3-82*x^4-100*x^5+30*x^6+35*x^7-x^8-2*x^9) (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]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
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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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