[seqfan] Re: OEIS Wiki: Offsets

[Benoît Jubin]

>> "Think long and hard whether a(0) is naturally defined. If yes, add it."

Among the first nine OEIS sequences, A000001(0)=0 and A000003(0)=0 should
therefore be added.

>> Back to the original subject, I think it is worth while mentioning the
example of sets & lists, and also insist on the example of general
functions defined from some given value on (which may be more often 0 than
1, but also something else).

I like to think that there are two big purveyors of integer sequences:
combinatorics and number theory. Sequences coming from combinatorics are
often defined for all natural numbers (for instance, the number of group
structures up to isomorphism on a set of size n) whereas sequences coming
from number theory are often defined (or at least, interesting) for nonzero
arguments, mainly because 0 is absorbing.

Benoit


On Mon, Apr 13, 2015 at 10:10 PM, M. F. Hasler <oeis at hasler.fr> wrote:

> On Mon, Apr 13, 2015 at 12:45 PM, Alonso Del Arte
> <alonso.delarte at gmail.com> wrote:
> > I do like how Felix elaborated the offset 3 example.
>
> I also appreciate the wish to make things, which are obscure for many
> OEIS users, more explicit.
>
> But I also agree with the rule :
>
> >> "Think long and hard whether a(0) is naturally defined. If yes, add it."
>
>
> >> The old text was shorter and clearer as well.
>
> shorter yes, but I think it's worth while adding examples.
>
> but regarding these, I ran into contradictions.
> E.g, the Planck time 5x10^-44 is cited for offset -44, but actually
> the offset is currently (maybe wrongly) -43.
> Personally, I think the current conventions for offset & indices for
> constants are a source of eternal confusion, it would be so simple and
> consistent to say that c = sum( i >= offset, a(i)*10^-i )
> [indices would be growing to +oo everywhere and would be equal to the
> position of the digit in the decimals of the number, which would be so
> natural...]
> but instead there are sometimes indices going from  offset  to  - oo
> (as they "should"), but sometimes (in the b-files and/or "list" page,
> IIRC the one shows the opposite of the other) they grow from offset to
> +oo, etc...
> What is more, there is no reasonable display of the constants ; if you
> click "constant" on the Planck time, if at least it would show
> 5.39... x 10 ^ -44  or  0.539... x 10 ^ -43
> or something alike, this would help. But currently it shows :  539106
>
>
> Back to the original subject, I think it is worth while mentioning the
> example of sets & lists, and also insist on the example of general
> functions defined from some given value on (which may be more often 0
> than 1, but also something else).
>
> --Maximilian
>
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