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A202388
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Digital root of Smith numbers A006753.
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4
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4, 4, 9, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 9, 4, 4, 6, 4, 6, 4, 4, 4, 4, 9, 3, 6, 4, 6, 6, 9, 6, 6, 9, 6, 4, 8, 9, 6, 4, 6, 6, 6, 4, 4, 6, 4, 4, 4, 6, 4, 4, 4, 4, 4, 6, 8, 9, 4, 6, 6, 4, 4, 4, 8, 9, 3, 4, 4, 6, 4, 9, 9, 4, 4, 9, 4, 9, 8, 9, 4, 4, 6, 9, 4, 4
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internal format)
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OFFSET
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1,1
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COMMENTS
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LINKS
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MATHEMATICA
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d[n_]:=IntegerDigits[n]; dr[n_]:= NestWhile[Total[d[#]]&, n, #>9&]; tr[n_]:=Transpose[FactorInteger[n]]; t1=Select[Range[4, 2.2*10^3], !PrimeQ[#]&&Total[d[#]]==Total[d@tr[#][[1]]*tr[#][[2]], 2]&]; Table[dr[n], {n, t1}] (* t1 gives Smith numbers - Jayanta Basu, Jun 04 2013 *)
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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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