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A199975
Multiplicative digital root of n-th prime.
3
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
OFFSET
1,1
LINKS
FORMULA
a(n) = A031347(A000040(n)).
MATHEMATICA
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 *)
CROSSREFS
Cf. A199976 (multiplicative digital root of n-th nonprime number).
Sequence in context: A113656 A007652 A060418 * A086355 A053666 A101987
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 13 2011
STATUS
approved