[seqfan] Re: List the dividers, sum the digits

[Veikko Pohjola]

Hi seqfans,

The following sequence is composed of numbers n such that the sum of digits of all divisors of n equals 15:
8, 14, 15, 20, 26, 59, 62, …
It actually depicts the positions of number 15 in A034690. 
Cute but maybe without much interest.

Veikko


M. F. Hasler kirjoitti 9.11.2015 kello 2.07:

> Eric,
> 
> I found that this is  A094501.
> I did not find at once this and
> A086793 = Iterate the map n -> sum of digits of all divisors of n (cf.
> A034690); sequence gives number of steps to reach 15.
> because I considered the version "...to reach a fixed point (1 or 15)"
> which starts with 1.
> I hope it will be accepted to change A086793 in order to prefix a(1)=1.
> 
> Maximilian
> 
> 
> On Sun, Nov 8, 2015 at 1:11 PM, Eric Angelini <Eric.Angelini at kntv.be> wrote:
>> 
>> Hello SeqFans,
>> Jean-Marc Falcoz has computed the
>> 22 first terms of the A(n) seq where
>> a(1) is the smallest integer looping in
>> 1 stage, a(2) the smallest looping in
>> 2 stages, a(3) in 3 stages, etc.
>> It seems that computing a(23) will
>> take a lot of time [the graph of A(n)
>> climbs exponentially after a(22)] --
>> not to say a(24)]. If someone wants
>> to give it a try and submit the seq to
>> the OEIS, please do...
>> Best,
>> É.
>> 
>> {1},
>> {8, 15},
>> {7, 8, 15},
>> {4, 7, 8, 15},
>> {3, 4, 7, 8, 15},
>> {2, 3, 4, 7, 8, 15},
>> {19, 11, 3, 4, 7, 8, 15},
>> {12, 19, 11, 3, 4, 7, 8, 15},
>> {6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {10, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {16, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {34, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {36, 46, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {66, 36, 46, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {162, 66, 36, 46, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {924, 168, 102, 36, 46, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15},
>> {71820, 1104, 168, 102, 36, 46, 18, 30, 27, 22, 9, 13, 5, 6, 12, 19, 11, 3, 4, 7, 8, 15}
> 
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