[seqfan] Re: Guided browsing of the OEIS based upon personal preferences?

Rick Shepherd rlshepherd2 at gmail.com
Sun Oct 25 18:06:30 CET 2009

...and thanks for your comments!

I *shouldn't* really spend the time right now to respond with the detail
your comments deserve -- but I do want to make a few, quick points:
1) I've also thought that this group might want to spend time discussing
potential new keywords (or, as you now say, categories -- although I'll
probably use the terms interchangeably below), at least for manual
attachment to entries.  I'm sure that different people have different
interests and needs here -- and that other people should have much more say
than me on this.
2) To agree with you at least on the need for a "non-" descriptor for
keywords:  Currently, for example, there is "fini" and absence of "fini"
which doesn't necessarily imply infinite, so there should at least be an
equally clear way to designate that a specific sequence is known to be
infinite.  I need to think longer about such things as "conj-", "unkn-", or
"bot-" (and/or even "bot-conj-") in a similar context.
3) I've spent several days earlier this year thinking of other ways (perhaps
non-traditional) of classifying sequences.  I'll list a few below (in 5).
4) Several months ago, I stumbled upon "PersonalBrain" software at
www.TheBrain.com <http://www.thebrain.com/>.
It creates and maintains databases, called "brains", full of "thoughts" (at
least 100,000 per brain :^), not sure what actual limit is).  The thoughts
can be connected like an arbitrary network, not necessarily requiring a
hierarchical structure.
During the free 30-day trial, I played around with connecting some of my
new, different sequence categories since some of the categories imply
membership in some other categories.  Then individual sequence numbers can
be listed more easily under all appropriate categories.  Even after the
trial expired, I can at least still access the brain's diagrams (I haven't
yet tried any new additions or modifications but this may be possible
still).  What is really interesting about this is that one can click on a
particular "thought" (which can have associated attachments, etc.,) and it
is brought front-and-center with the entire local context of the network of
thoughts redrawn around it (plus normal backward and forward keys exist plus
ability to directly access any particular thought by (partial) string
searches).  Anyway, you get the idea about the general flexibility that this
has for indexing just about anything....  (I may be able to show a picture
of one of these screens but I know I shouldn't put it here in this list.).
5) Some other possible categories (not all of equal importance and some
implying others or existing keywords; some may overlap or be identical to
yours, I don't have time to check right now):
all terms are constant
alternating signs
each term appears a finite number of times
each term appears an infinite number of times
each term is composite
each term is prime
non-increasing (vs strictly decreasing)
non-decreasing (vs strictly increasing)
all terms are bounded above
all terms are bounded below
terms based upon words of language XYZ
parity is odd
parity is even
(more generally) all terms are congruent to j mod k
(maybe even) terms have same number of digits
(maybe even) terms are all base n digits
etc., etc.
[Of course, with text searches available there are alternate ways of doing
this -- but to make searching easier agreed-upon and enforced methods would
be necessary]

I think you've definitely helped start a discussion worth having.


P.S.  I didn't address your comments in "B" about analogues -- but this
would be a very valuable feature certainly (but also requiring more manual

P.P.S.  I see that Franklin's just posted a message but I haven't read

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