A128212 a(n) = Sum_digits(p), where p is the product of the digits of n.

1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 2, 4, 6, 8, 1, 3, 5, 7, 9, 0, 3, 6, 9, 3, 6, 9, 3, 6, 9, 0, 4, 8, 3, 7, 2, 6, 10, 5, 9, 0, 5, 1, 6, 2, 7, 3, 8, 4, 9, 0, 6, 3, 9, 6, 3, 9, 6, 12, 9, 0, 7, 5, 3, 10, 8, 6, 13, 11, 9, 0, 8, 7, 6, 5, 4, 12, 11, 10, 9, 0, 9, 9, 9, 9, 9, 9, 9, 9, 9, 0

Offset

1,2

Comments

The sequence grows very slowly. For n <= 10000 the maximal value is 27.

Links

Marius A. Burtea, Table of n, a(n) for n = 1..6000

Formula

a(n) = A007953(A007954(n)). - Michel Marcus, Jun 07 2019 [Corrected by Sean A. Irvine, Sep 26 2023]

Example

a(73) = 3 because 7*3 = 21 and 2+1 = 3.

Maple

P:=proc(n) local i, k, w; for i from 1 by 1 to n do w:=1; k:=i; while k>0 do w:=w*(k-(trunc(k/10)*10)); k:=trunc(k/10); od; k:=w; w:=0; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; print(w); od; end: P(100);

Mathematica

Table[Total[IntegerDigits[Times@@IntegerDigits[n]]], {n, 100}] (* Harvey P. Dale, Feb 08 2013 *)

Prog

(Magma) [&+Intseq((&*(Intseq(n)))):n in [1..100]]; // Marius A. Burtea, Jun 06 2019
(PARI) a(n) = sumdigits(vecprod(digits(n))); \\ Michel Marcus, Jun 07 2019

Crossrefs

Cf. A007953, A007954.

Sequence in context: A371281 A031347 A087471 * A187844 A007954 A079475

Adjacent sequences: A128209 A128210 A128211 * A128213 A128214 A128215

Keyword

easy,nonn,base

Author

Paolo P. Lava and Giorgio Balzarotti, May 03 2007

Status

approved