[seqfan] Re: Canonical bijection from positive integers to positive rationals.
njasloane at gmail.com
Tue Mar 3 19:05:22 CET 2020
There is an entry in the Index to the OEIS, Section Ra, under "rational
numbers" which lists several of these bijections.
Peter or Frank, could you please expand this Index entry with any bijective
mappings that are not there.
And also add a link to the index entry to all of these sequence.
The link should say:
<a href="/index/Ra#rational">Index entries for sequences related to
enumerating the rationals</a>
By the way, there are also cross-references to this Index entry from
entries in the Index for "Bijection ..." and "Enumerating ..."
Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com
On Tue, Mar 3, 2020 at 10:17 AM Peter Munn <techsubs at pearceneptune.co.uk>
> Update: Having found another nice bijection in A229994(n)/A077610(n), I
> have listed this and others mentioned in this thread in the crossrefs for
> If seqfans add any other bijective mappings that are in OEIS, then at some
> point these can be copied to the other sequences.
> Best Regards,
> On Mon, March 2, 2020 8:08 pm, Peter Munn wrote:
> > On Mon, March 2, 2020 4:58 pm, Peter Luschny wrote:
> >> NS> For me, without doubt, the best map is the classic map based NS> on
> the Stern's diatomic series (or Stern-Brocot sequence, A002487. For me
> it is the Euclid tree: A295515.
> > I cast my vote for the Sagher map, A071974(n)/A071975(n), which is
> > multiplicative.
> > Best Regards,
> > Peter
> >> NS> from 1858: Look at all the references there.
> >> Let's wait and see. In 160 years, we can count references again. If you
> have Maple you can also try this delightful implementation:
> >> magic := x -> 1/(1 + floor(x) - frac(x)):
> >> And then run:
> >> 0; do magic(%) od;
> >> Cheers, Peter
> >> --
> >> Seqfan Mailing list - http://list.seqfan.eu/
> > --
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