A199976 Multiplicative digital root of n-th nonprime number.

1, 4, 6, 8, 9, 0, 2, 4, 5, 6, 8, 0, 2, 4, 8, 0, 2, 4, 6, 0, 6, 9, 2, 5, 8, 8, 4, 0, 8, 6, 0, 8, 6, 8, 0, 5, 0, 0, 0, 0, 5, 0, 0, 2, 8, 8, 0, 8, 6, 0, 0, 4, 6, 5, 8, 8, 0, 0, 8, 6, 6, 0, 6, 0, 8, 0, 9, 8, 4, 8, 0, 0, 4, 8, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 5, 6

Offset

1,2

Links

Table of n, a(n) for n=1..86.

Formula

a(n) = A031347(A018252(n)).

Mathematica

mdr[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; mdr/@Select[Range[200], !PrimeQ[ #]&] (* Harvey P. Dale, Aug 18 2024 *)

Crossrefs

Cf.: A199975(n) = multiplicative digital root of n-th prime.

Sequence in context: A183005 A103189 A083786 * A165957 A338028 A110750

Adjacent sequences: A199973 A199974 A199975 * A199977 A199978 A199979

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved