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 A094450 Number of iterations of the sum of digits of the divisors of 10^n needed to reach 15. 1
 12, 10, 16, 15, 3, 11, 4, 13, 6, 6, 5, 19, 16, 3, 11, 13, 19, 7, 5, 9, 6, 16, 16, 19, 5, 3, 12, 3, 18, 16, 4, 10, 6, 16, 18, 12, 4, 16, 12, 13, 12, 5, 12, 5, 20, 15, 16, 12, 4, 16, 4, 20, 5, 19, 4, 6, 21, 5, 6, 5, 21, 12, 5, 16, 13, 17, 6, 5, 7, 21, 20, 18, 12, 10, 6, 18, 13, 13, 6, 13, 15 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..1400 MATHEMATICA Table[Length[NestWhileList[Total[Flatten[IntegerDigits/@Divisors[#]]]&, 10^n, #!= 15&]]-1, {n, 90}] (* Harvey P. Dale, Mar 05 2019 *) PROG (Python) from sympy import divisors def sd(n): return sum(map(int, str(n))) def f(n): return sum(sd(d) for d in divisors(n, generator=True)) def a(n): i, c = 10**n, 0 while i != 15: i = f(i); c += 1 return c print([a(n) for n in range(1, 82)]) # Michael S. Branicky, Dec 10 2021 CROSSREFS Cf. A034690, A086793. Sequence in context: A140267 A343530 A262965 * A307166 A297910 A298503 Adjacent sequences: A094447 A094448 A094449 * A094451 A094452 A094453 KEYWORD base,nonn AUTHOR Jason Earls, Jun 04 2004 STATUS approved

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Last modified September 26 04:29 EDT 2023. Contains 365653 sequences. (Running on oeis4.)