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A199975
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Multiplicative digital root of n-th prime.
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3
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2, 3, 5, 7, 1, 3, 7, 9, 6, 8, 3, 2, 4, 2, 6, 5, 0, 6, 8, 7, 2, 8, 8, 4, 8, 0, 0, 0, 0, 3, 4, 3, 2, 4, 8, 5, 5, 8, 8, 2, 8, 8, 9, 4, 8, 8, 2, 2, 6, 8, 8, 0, 8, 0, 0, 8, 0, 4, 4, 6, 6, 0, 0, 3, 9, 2, 9, 8, 6, 0, 0, 5, 2, 8, 4, 4, 2, 4, 0, 0, 8, 8, 2, 8, 0, 6
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n) = A031347(A000040(n)).
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MATHEMATICA
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Table[s = Prime[n]; While[s >= 10, s = Times @@ IntegerDigits[s]]; s, {n, 100}] (* T. D. Noe, Nov 15 2011 *)
Table[NestWhile[Times@@IntegerDigits[#]&, p, #>9&], {p, Prime[Range[90]]}] (* Harvey P. Dale, Jul 31 2020 *)
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CROSSREFS
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Cf. A199976 (multiplicative digital root of n-th nonprime number).
Sequence in context: A113656 A007652 A060418 * A086355 A053666 A101987
Adjacent sequences: A199972 A199973 A199974 * A199976 A199977 A199978
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KEYWORD
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nonn,base
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AUTHOR
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Jaroslav Krizek, Nov 13 2011
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STATUS
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approved
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