[seqfan] Re: K(n)—>a(n).

[David Sycamore]

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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>>> Seqfan Mailing list - http://list.seqfan.eu/
>> 
>> 
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