[seqfan] Re: K(n)—>a(n).

[Neil Sloane]

well, maybe I overreacted.


On Wed, Dec 11, 2019 at 3:09 AM David Sycamore via SeqFan <
seqfan at list.seqfan.eu> wrote:

> My post was simply a draft idea made in good faith to a forum whose
> purpose is to promote friendly discussions about sequences. Therefore why
> should any well intended submission receive such a dismissive and
> exaggerated response as mine did?
>
> If Seqfans wants a culture where disparaging remarks are encouraged, then
> good luck getting people to share their ideas here in future.
> Best regards,
> David.
>
>
>
> > On 10 Dec 2019, at 18:37, Ali Sada via SeqFan <seqfan at list.seqfan.eu>
> wrote:
> >
> > Dear Dr. Sloane,
> > As a new comer to the OEIS, I didn't think much of the "base-10"
> sequences. They seemed easy and superficial and didn't look like "real
> math" to me. But following up closely on some of these sequences in the
> OEIS, I realized that such sequences have actually more layers of
> difficulty. Finding relationships between the "values" of numbers and their
> "shapes" is not superficial. The familiarity with the digits 0 to 9
> concealed this fact from me for some time.
> >
> > When I suggested two base-10 sequences and asked questions about them,
> the responses from David Seal and Dr. Hasler were eye opening, to say the
> least. I think their analyses are worthy of the OEIS, regardless of the
> fact that original ideas of the two sequences seemed banal.
> >
> > I have already added one of these two sequences to the OEIS (A328326).
> After reading your email, I instantly tried to delete it but didn't know
> how.
> >
> > Best Regards,
> > Ali
> >
> >
> >> On Tuesday, December 10, 2019, 12:15:05 PM EST, Neil Sloane <
> njasloane at gmail.com> wrote:
> >>
> >> For integer n let K(n) be the permutation of the digits of n formed by
> > sequentially combining the greatest and smallest digits in adjacent pairs
> > ...
> >
> > I have to say that this sentence makes me feel ill.  There are better
> > things to think about than playing with the digits of n.
> >
> > Unless you want to generate more examples for the "Examples of what not
> to
> > submit" list.
> >
> >
> > On Tue, Dec 10, 2019 at 10:32 AM David Sycamore via SeqFan <
> > seqfan at list.seqfan.eu> wrote:
> >
> >> Mistake; a(13)=63 not 9. Hope there are no more....
> >> David.
> >>
> >>>> On 10 Dec 2019, at 14:29, David Sycamore via SeqFan <
> >>> seqfan at list.seqfan.eu> wrote:
> >>>
> >>> For integer n let K(n) be the permutation of the digits of n formed by
> >> sequentially combining the greatest and smallest digits in adjacent
> pairs
> >> until running out of digits to play with. Examples: K(1)=1, K(10)=10,
> >> K(123)= 312, K(277272)=727272, K(539204)=905243.
> >>>
> >>> (Definition is draft, suggestions to improve it are  welcome).
> >>>
> >>> We compute a(n) as follows:
> >>> Take the absolute difference |n-K(n)| to get a new number. Repeat the
> >> process with that number until reaching a number m for which K(m)=m,
> then
> >> a(n)=m.
> >>>
> >>> I get (by hand, so could be some bugs)
> >>>
> >>> 0,1,2,3,4,5,6,7,8,9,10,11,9,9,9,9,9,54,63,72,20,21,22,9,63,9...
> >>>
> >>> Could there be some n for which the above trajectory loops? If so then
> >> how to define a(n)? (I have not found any such n yet..).
> >>>
> >>> A curious feature seems to be that if a(n) is other than n, then it is
> a
> >> multiple of 9, but I have not confirmed the veracity of this.
> >>>
> >>> Sequence does not seem to be in oeis
> >>>
> >>> Any interest in this?
> >>> Best
> >>> David.
> >>>
> >>> ps: Unless I am  mistaken a(123)=63, a(1234)=81, a(4321)=63,
> >> a(12345)=70434.
> >>>
> >>>
> >>>
> >>> --
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> >>
> >>
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> >
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