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 A128212 a(n) = Sum_digits(p), where p is the product of the digits of n. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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) = A007954(A007953(n)). - Michel Marcus, Jun 07 2019 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: A062078 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

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Last modified June 1 13:11 EDT 2020. Contains 334762 sequences. (Running on oeis4.)