OEIS gripes

[Olivier Gerard]

On Fri, Jul 06, 2001 at 02:02:26PM -0400, David W. Wilson wrote:
> 
> I was looking at some of your recent sequences.  Many are incorrect,
> duplicates, or unjustifiably short sequences (easily filled out).
> 

Your reaction is to my opinion most welcome, but the "your" is a bit
misleading as the first 8 sequences you quote are from someone who 
is not on the seqfan list (Mr Amarnath Murthy).

> As much as I love the OEIS, it looks as if it is becoming a dumping
> ground for some very poor-quality stuff in terms of correctness and
> relevancy.  The OEIS would certainly benefit from a review process.
> 

Neil is the final authority on what goes into the EIS, but in the same
time, he cannot do everything without slowing many aspects of this
database in the process or spending so much time on it that he cannot
continue just breathing, eating, doing his personal research...

The purpose of the seqfan mailing list is precisely to help interested
and devoted people work together to enhance and edit the EIS.
Many on this list have long mail threads with Neil while improving many
sequences every week.  

> To underscore my point, here is an analysis of some sequences from
> the recent sequences list:
> 

I engage everyone on the seqfan list who is not doing that already
to read the recent.txt file regularly on the site and look after
possible improvements.

I point out that I am the author of none of the sequences quoted by David.

> ------------------------------------------------------------------------
> A062931 to A062938

(I agree with all your comments on these ones above)

> A060648 has a difficult description as a multiplicative function.
> I am guessing that it is multiplicative with
>     f(p^e) = 1 if e = 0, p*f(p,e-1)+2 if e >= 1.
> If so, it easily extends to
> 1 4 5 10 7 20 9 22 17 28 13 50 15 36 35 46 19 68 21 70 45 52 25 110 37
> 60 53 90 31 140 33 94 65 76 63 170 39 84 75 154 43 180 45 130 119 100
> 49 230 65 148 95 150 55 212 91 198 105 124 61 350 63 132 153 190 105
> 
And there are plenty of references I think many were planning to add.

> A062004 is correct, questionably relevant.
> 
> A062007 is correct, questionably relevant.
>
It would be nice if there was a motivation for these two.
Even nicer to add code to the superseeker so that those kind of sequences
could be identified.

> A062008 is interesting.
> 
> A062039 is really pi(n!).  I added two elements.  I assume someone
> with a boss pi(n) algorithm could easily add a few more.
> 0 0 1 3 9 30 128 675 4231 30969 258689
> 

> A062274 I was able to extend a little:
> 0 0 1 7 45 291 2030 15695 135045 1287243 13495669
> 
> A062282 has a formula.  We ought to be able to extend it easily.
> 
> A062304 was easy to extend a few elements:
> 0 0 1 1 2 2 5 3 8 11 22 25 53 76 151 244 435 749 1314 2367 4239 7471
> 13705
> 
The EIS is a collaborative work, leaving at first a sequence not as 
extended as it could be is not a sin.  I have myself experienced the
following: having submitted the first 20 terms of a sequence, planning
to extend it the day after, with a larger computer, I saw that it had
been extended in the meantime.


> A062307 should not include 1.  When it is removed, it become A000469.
>
I agree with that. A good practice is to remove all leading 1 and 0 when doing lookups.
But again, even careful contributors happen to make mistakes. The comment system
is there for that purpose.

If you look carefully to the EIS, you will see that there is a number of 'dead' sequences
a little more than one hundred and a score, which were droped for duplication or bad definition.
Sometimes it was just a matter of a leading term.

I can testify that Neil looks very carefully to problems of offset, leading terms,
correct number-theoretical definitions.


Olivier Gerard