[seqfan] Re: As much as I hate "base" sequences...

[David Wilson]

Ouch, this sequences if full of chuff.
Even the visible values are mostly -1.

A much better sequence would be "Number of steps for A114440(n) to reach 1".
This would skip the values that never reach 1.
It would be much better use of OEIS real estate.
In fact, the sequence would be finite, and all the interesting elements
could be included in a b-file.
Hans could pound out a b-file in no time.

As much as I hate "base" sequences, I hate sequences with "or -1 if
undefined" even more.
If the OEIS supported index sequences, we could create your sequence above
with index sequence A114440.
Then you could submit only the values at elements of A114440.

> -----Original Message-----
> From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of M. F.
> Hasler
> Sent: Wednesday, January 22, 2014 4:34 PM
> To: Sequence Fanatics Discussion list
> Subject: [seqfan] Re: As much as I hate "base" sequences...
> 
> On Sat, Jan 18, 2014 at 1:49 PM, Neil Sloane <njasloane at gmail.com> wrote:
> > another version which is also nice: restrict the search to numbers
> > which eventually reach 1.
> > Of those, take the smallest that takes n steps to reach 1. That is a(n).
> 
> It seems that no-one yet submitted a(n) = Number of iterations of A235600
> to reach 1 when starting with n, or -1 if 1 is never reached, where
A235600(x)
> = x/sum_of_digits(x) if this is an integer, else x.
> 
> So I propose it as https://oeis.org/draft/A236338
> 
> Maximilian
> 
> 
> 
> > On Fri, Jan 17, 2014 at 7:26 PM, David Wilson
> <davidwwilson at comcast.net>wrote:
> >
> >> Start with k and repeatedly apply the function
> >>
> >> k -> k / sum of digits of k
> >>
> >> stopping when there is a positive remainder or the divisor is 1.
> >>
> >> The smallest survivors of n iterations among the 29-smooth numbers
> >> are
> >>
> >> 0 1
> >> 1 2
> >> 2 12
> >> 3 108
> >> 4 1944
> >> 5 52488
> >> 6 1102248
> >> 7 44641044
> >> 8 1008000000
> >> 9 10080000000
> >> 10 100800000000
> >> 11 1008000000000
> >> 12 10080000000000
> >> 13 100800000000000
> >> 14 1008000000000000
> >> 15 10080000000000000
> >> 16 100800000000000000
> >> 17 1008000000000000000
> >> 18 10080000000000000000
> >>
> >> I am all but certain that these are these are indeed the smallest
> >> survivors among the integers, and that the sequence extends to
> >> infinity in the obvious way.
> >>
> >> The change in behavior at a(8) surprised me at first. a(1) through
> >> a(7) eventually reach 1.  For n >= 8, we have
> >>
> >> a(n) = 1008*10^(n-2) ->  112*10^(n-2) -> 28*10^(n-2) -> 28*10^(n-3) ->
...
> >> -> 28.
> >>
> >> ending at 28 after n iterations.
> 
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