[seqfan] Re: Primes from Indices of Pi and E

Wed Apr 25 09:00:23 CEST 2012

Encyclopedia as a survey of integer sequences is different from that of the 
words of a natural language in that the number of words is not infinite. 
That is why the latter can be comprehensive but the former cannot. From the 
user's point of view it is highly desirable that all possible entries are 
included but that cannot be the goal with an encyclopedia of sequences. My 
concern was rather would it be possible to rationalize OEIS such that both 
the user and a potential contributor were guided to a higher level of 
hierarchy to search for the potential sequence class or the super-sequence 
from which he could make his own reasoning as for the nature of his entry.
Veikko Pohjola

----- Original Message ----- 
From: "Neil Sloane" <njasloane at gmail.com>
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Sent: Tuesday, April 24, 2012 6:26 PM
Subject: [seqfan] Re: Primes from Indices of Pi and E

> There are other reasons to include a sequence in the OEIS, besides
> the ones mentioned by Charlie.
>
> People often search the OEIS for sequences with some desirable property.
> They don't know the terms of the sequence beforehand, but
> they know what property they are looking for.
>
> For example, sequences which look random but have a simple
> mathematical definition - or low Kolmogorov complexity. Like
> the one related to the digits of e and pi that started this discussion.
>
> We should be tolerant and broadminded - at least where the OEIS is
> concerned!
>
> Neil
>
> On Tue, Apr 24, 2012 at 11:09 AM, Charles Greathouse <
> charles.greathouse at case.edu> wrote:
>
>> > I would like to have the discussion more general about what should not 
>> > be
>> > included in OEIS.
>>
>> I think this is a fascinating and difficult question.
>>
>> The underlying philosophy, in my view, is that sequences are included
>> to help others who come across them later.  So one essential trait is
>> that either someone will search for that sequence later, or else the
>> sequence will be referenced elsewhere in a place which (1) interested
>> people read, and (2) is sufficiently interesting to those at that
>> place that some will follow the link to the sequence.  Perhaps a
>> sequence is sufficiently esoteric that no person will ever search for
>> it directly, but it has a deep link to another sequence which is
>> searched for, and is given there in a comment (or at least a
>> cross-reference).
>>
>> Another essential trait that follows from this philosophy is that the
>> sequence should contain information.  It's a real letdown to search in
>> the OEIS for a sequence only to find it, but have nothing other than
>> the terms you had already calculated.  Of course for some sequences
>> just finding the terms is hard, and providing those is perhaps
>> sufficient.
>>
>> Any other ideas as to 'first-principles' on inclusion?
>>
>> On a more practical level, I should mention
>> https://oeis.org/wiki/User:Alonso_del_Arte/Is_this_sequence_interesting
>> which contains specific advice on what to include (and, more to the
>> point, what not to include).  As far as your examples go, A052378
>> seems fine to me.  Your hypothetical subsequence of A210582 is (I
>> agree) a bit much.
>>
>> Charles Greathouse
>> Analyst/Programmer
>> Case Western Reserve University
>>
>> On Tue, Apr 24, 2012 at 4:24 AM, Veikko Pohjola <veikko at nordem.fi> wrote:
>> > Dear Seqfans,
>> >
>> >
>> >
>> > I would like to have the discussion more general about what should not 
>> > be
>> > included in OEIS. There are, for instance, numerous sequences in OEIS,
>> which
>> > are just instances of a given class of sequence, which can reproduce
>> itself
>> > in infinitely many different ways. The fact that some have been 
>> > published
>> > cannot mean that any other instance of the class should. How about
>> > sub-sequences, should they be excluded and on what basis?
>> >
>> >
>> >
>> > A couple of examples.
>> >
>> >
>> >
>> > In A052378 the prime quadruples follow the gap pattern [4,2,4], but 
>> > there
>> > are (obviously infinitely many) other gap patterns which produce all 
>> > the
>> > sequences, some of which (like those listed as cross references of
>> A078854)
>> > are in OEIS. I cannot see any publication policy to justify why those
>> now in
>> > OEIS are there. The general pattern [a,b,c] is known, however, by which
>> the
>> > class itself is defined and can be exploited to cover all its 
>> > instances.
>> >
>> >
>> >
>> > The recent A210582 is the numbers whose first digit is the remainder of
>> > their division by the last digit. Should the sub-sequence, where
>> "numbers"
>> > is replaced by "primes" be included. I think it should not.
>> >
>> >
>> >
>> > Best regards,
>> >
>> > Veikko
>> >
>> >
>> >
>> > ----- Original Message ----- From: "T. D. Noe" <noe at sspectra.com>
>> > To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
>> > Sent: Monday, April 23, 2012 10:46 PM
>> > Subject: [seqfan] Re: Primes from Indices of Pi and E
>> >
>> >
>> >> My two cents: No.
>> >>
>> >> At 3:40 PM -0400 4/23/12, Harvey P. Dale wrote:
>> >>>
>> >>>           This sequence gives the indices at which a single digit of
>> >>> Pi plus a single digit of E sum to a prime: 
>> >>> 1,3,5,6,7,9,10,12,14,15,19
>> .
>> >>> . .  For example, the 5th digit of Pi is 5, the fifth digit of E is 
>> >>> 2,
>> >>> and 5+2 = 7.  It is easy to generate other similar sequences.  For
>> >>> example, this sequence gives the indices starting at which the next 
>> >>> ten
>> >>> digits of Pi (read as a number) plus the next ten digits of E (again
>> >>> read as a number) sum to a prime:
>> >>> 1,6,22,32,119,123,146,152,189,216,230,255 . . .
>> >>>
>> >>>
>> >>>
>> >>>           Is any of this worth putting into the OEIS?
>> >>>
>> >>>
>> >>>
>> >>>           Best,
>> >>>
>> >>>           Harvey
>> >>>
>> >>>
>> >>> _______________________________________________
>> >>>
>> >>> Seqfan Mailing list - http://list.seqfan.eu/
>> >>
>> >>
>> >> _______________________________________________
>> >>
>> >> Seqfan Mailing list - http://list.seqfan.eu/
>> >>
>> >
>> >
>> > _______________________________________________
>> >
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>>
>> _______________________________________________
>>
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>
>
>
> -- 
> Dear Friends, I will soon be retiring from AT&T. New coordinates:
>
> Neil J. A. Sloane, President, OEIS Foundation
> 11 South Adelaide Avenue, Highland Park, NJ 08904, USA
> Phone: 732 828 6098; home page: http://NeilSloane.com
> Email: njasloane at gmail.com
>
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