Uncertain sequences (was Re: TR : Re : The OEIS will be on holiday for the rest of the year!)

[Alexandre Wajnberg]

>> Alexandre:
>>And why are at least no less interessant sequences than supra not accepted?
>>(ex: 1903, 2303, 2307, 2311, 2315... "Exceptional years of 23rd december's
>>winter solstice since the beginning of the Gregorian Calendar in 1582" is no
>>less interessant than a "word" sequence).

Me 
As I said earlyer, actually I didn't submit it because of the moratorium in
december. But I will -Thanx Neil


>>Jaap:
>>Calculating solstices (and other phenomena) in the far future
>>is uncertain because of the unpredictable earth rotation.

Yes uncertain but in a very far future! Although such sequences are infinite
by definition (actually not!: max n = more or less 5.10^9, when the Sun will
blast in a red giant star and "eat" the Earth), we know their relevancy is
limited, say, to a few centuries from now on... So, such a sequence could be
"tackled" from another point of vue: not the *values* a(n) (i.e. "are they
correct for all n's"), but *n*: the domain of validity of such sequences,
domain we have to define.
So...:

>>Jaap
>>What is the DELTA T (...) DELTA T now is
>approximately 65 s, but what will it be in the year 3000?
>There is another uncertain factor in the calculations and that is
>the planetary model. Some calculations use the VSOP 87 model and
>others depend on the JPL ephemerides from NASA.

Right, the definition should be more precise. These dates are published by
IMCCE - Institut de Mécanique Céleste et de Calcul des Éphémerides, but the
informations (DELTA T etc) are not explicite there:

http://www.imcce.fr/page.php?nav=en/ephemerides/astronomie/saisons/presentat
ion_saisons.php

If you have easy accessible information and would like to submit...

> Brendan
> There is in fact an algorithm
> for computing it correctly - wait for each event to happen.  This
> is a rather slow algorithm, but an algorithm nevertheless.

Like for the sequence, I don't remember the number, which goes so:
1,2,3,4,5,6,7,8.....29,30,31,31,31,31,31...:  "the years of the life of Mr
Smith, f(t)".
It's not only a joke, but an exemple of sequences defined in the past, which
is the case for this astronomical sequences. (Smith is defined in the future
also but it's trivial)

Jaap
There is one sure entry: 1903. But not in Russia where the Gregorian
calendar
was introduced in 1918!

Correct. But it doesn't matter what calendar is in use here or there since
the definition <gregorian calendar> implies peoples and countries which are
using it.


Thanx for documented questioning and interest. I'll let you know when I'll
complete the job (at least my part of) or need help.


Alexandre



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