A199975 Multiplicative digital root of n-th prime.

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A199972 A199973 A199974 * A199976 A199977 A199978

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved