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A202388
Digital root of Smith numbers A006753.
4
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
OFFSET
1,1
COMMENTS
a(n) = A010888(A006753(n)); range = {4,6,8,9}.
LINKS
Eric Weisstein's World of Mathematics, Smith Number
Wikipedia, Smith number
MATHEMATICA
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 *)
CROSSREFS
Sequence in context: A272427 A068340 A097667 * A283919 A283670 A019627
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Dec 19 2011
STATUS
approved