[seqfan] Re: SeqFan Digest, Vol 42, Issue 7
njasloane at gmail.com
Tue Mar 20 19:57:41 CET 2012
This seems like an excellent idea!
Rather than putting this information into the %O line, however,
another possibility, requiring fewer changes to the existing set-up,
might be to put the information into the %Y (cross-references) section,
by adding a line saying
%Y A000040 Indexed by A000027
%Y A007318 Indexed by A003056, A002262
On Tue, Mar 20, 2012 at 2:42 PM, Antti Karttunen
<antti.karttunen at gmail.com>wrote:
> On Sun, Mar 18, 2012 at 9:23 PM, <seqfan-request at list.seqfan.eu> wrote:
> My proposal is to modify the current %O entry to specify of one or more
> index sequences. For instance, the %O line of A000040 (the prime
> numbers) would become:
> %O A000040 A000027
> This says that A000040 is indexed on A000027 (the nonnegative integers).
> Thus we have
> n = A000027 1 2 3 4 5 6 7 ...
> a(n) = A000040 2 3 5 7 11 13 17 ...
> This is much prettier and more general that the current scheme, which
> allows only consecutive indices. For instance, we can now express that
> A003649 is indexed on the squarefrees by stating:
> %O A003649 A005117
> For tables, we give a %O line with two index sequences. For instance:
> %O A007318 A003056 A002262
> x = A003056 0 1 1 2 2 2 3 ...
> y = A002262 0 0 1 0 1 2 0 ...
> a(x,y) = A007318 1 1 1 1 2 1 1 ...
> This approach allows us to build free-form tables of any dimension. It
> transforms the integer sequence database to an integer function database,
> which is really what we want if we are including tables.
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