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A051802
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Nonzero multiplicative digital root of n.
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34
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1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 2, 4, 6, 8, 1, 2, 4, 6, 8, 3, 3, 6, 9, 2, 5, 8, 2, 8, 4, 4, 4, 8, 2, 6, 2, 8, 6, 6, 8, 5, 5, 1, 5, 2, 1, 3, 5, 4, 2, 6, 6, 2, 8, 8, 3, 8, 8, 6, 2, 7, 7, 4, 2, 6, 5, 8, 8, 3, 8, 8, 8, 6, 8, 6, 4, 6
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| Discussed Jun 15 1991 on sci.math by Mayne, Rusin, Landrum et al.
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LINKS
| T. D. Noe, Table of n, a(n) for n=0..1000
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FORMULA
| If n==A051801(n) then n else a(A051801(n)).
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MAPLE
| A051801 := proc(n) local d, j: d:=convert(n, base, 10): return mul(`if`(d[j]=0, 1, d[j]), j=1..nops(d)): end: A051802 := proc(n) local m: if(n=0)then return 1:fi: m:=n: while(length(m)>1)do m:=A051801(m): od: return m: end: seq(A051802(n), n=0..100); # Nathaniel Johnston, May 04 2011
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MATHEMATICA
| mdr0[n_] := NestWhile[Times @@ (IntegerDigits@# /. 0 -> 1) &, n, UnsameQ, All]; Table[ mdr0@n, {n, 0, 104}] - Robert G. Wilson v (rgwv(at)rgwv.com), Aug 04 2006
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PROG
| (Haskell)
a051802 = until (< 10) a051801 -- Reinhard Zumkeller, Nov 23 2011
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CROSSREFS
| Uses A051801.
Sequence in context: A054055 A067456 A052429 * A051801 A071205 A066750
Adjacent sequences: A051799 A051800 A051801 * A051803 A051804 A051805
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KEYWORD
| nonn,easy,base,nice
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AUTHOR
| Dan Hoey (Hoey(AT)AIC.NRL.Navy.Mil), Dec 09 1999
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EXTENSIONS
| Occasionally defined with a(0)=0.
More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Aug 04 2006
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