[seqfan] Re: Another planetary sequence
Frank Adams-Watters
franktaw at netscape.net
Sun Sep 11 21:19:33 CEST 2016
There are a certain number of time-dependent sequences already in the database. We don't want them to be more than a small minority. So the default at this point is to reject such unless there is some really good reason to include them.
Franklin T. Adams-Watters
-----Original Message-----
From: Rick Shepherd <rlshepherd2 at gmail.com>
To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
Sent: Sun, Sep 11, 2016 2:12 pm
Subject: [seqfan] Re: Another planetary sequence
Regarding the original question, I'd just like to point out that many OEISsequences are time dependent, say, on how many days in an Earth year --which will certainly change eventually. Also, many physical "constants" mayturn out not to be (in time and/or space) after more refined understandinglater. Nevertheless, snapshots of current understanding are definitelyuseful.A category of planet-related sequences of interest (in general to me, andcombinatorially) is number of types of planetary/star/moon orbital systems,probably under various simplifying assumptions (the 3-body problem havingnot been solved yet).I have thought about such sequences several times over the last (10+?)years, haven't submitted anything yet, but think they would be ofincreasing general interest now that exoplanet discoveries have acceleratedmarkedly.For simplicity, maybe start with counting all orbital situations that canoccur with all orbits elliptical and coplanar... Moons can have moons, etc.Include rotations or not. Retrograde orbits or not. Well-definingequivalence classes of orbital systems may be a bit tricky still.(I'm deliberately ignoring Figure-8 orbits and such for now.)Anyway, I think this is fertile ground (for the OEIS at least) for anytakers.Best regards,Rick--Seqfan Mailing list - http://list.seqfan.eu/
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