[seqfan] Re: automatic cross-refence

David Wilson dwilson at gambitcomm.com
Tue Mar 3 16:43:52 CET 2009

I always thought it might be nice to have floating references.

When someone submits a line that references multiple sequences, such as

%F A000101 a(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)

At submission time, a() references are expanded, and a multi-sequence
entry added to the raw database:

%F A****** A000101(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)

At database update time, this line is expanded for all referenced
sequences, and a() references restored:

%F A000101 A000101(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)
%F A002386 A000101(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)
%F A005250 A000101(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)
%F A008995 A000101(n) = A002386(n) + A005250(n) - A008995(n) + 1 (M. Hasler)

Max Alekseyev wrote:
> On Mon, Mar 2, 2009 at 9:17 PM, Dmitry Kamenetsky
> <Dmitry.Kamenetsky at nicta.com.au> wrote:
>
>> Dear Seqfans,
>>
>> I often see two sequences A and B, where A references B, but B does not
>> reference A. This means that a person reading B will have a hard time
>> finding A.
>>
>
> Not a problem at all - a regular search of B in the OEIS will return,
> in particular, the sequence A (since it contains a reference to B in
> its body).
>
> Is it possible to have an automatic cross-reference engine
>
>> that completes these missing references? The idea is the following, for
>> each pair (A, B):  if A->B exists, but B->A doesn't exist then add a
>> cross-reference to A from B.
>>
>
> This idea was discussed a couple of times before.
> A short answer is NO, it won't work.
> The problem is that some sequences are highly referenced and
> referencing back every sequence will blow up them.
> Here is example: A000040 is referenced by more than 2,500 sequences -
> just imagine how much space it would take to reference them all back.
>
> Regards,
> Max
>
>
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