[seqfan] Re: Suggestions for A300000 ?

Neil Sloane njasloane at gmail.com
Fri Feb 23 01:17:40 CET 2018


Sean,  Sounds like an interesting sequence!  Please go ahead and submit it,
and tell me the A-number.


Best regards
Neil

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 Thu, Feb 22, 2018 at 5:42 PM, Sean A. Irvine <sairvin at gmail.com> wrote:

> I have a potential candidate for A300000.  A triangle based on J. H.
> Conway's values from A007972 to A007975.  Essentially these sequences are
> about how many permutations of 1,2,...n can be reached in a given number of
> "block reversals" where a block reversal consists of reversing 2 or more
> consecutive values in the permutation.  I'll be extending some of those
> sequences soon with extra values, but a triangle for this problem (which I
> don't think is currently present in the OEIS) starts:
>
> 1
> 1, 1
> 1, 3, 2
> 1, 6, 15, 2
> 1, 10, 52, 55, 2
>
> Each row sums to n!, T(n,k), k>=0, is the number of permutations of length
> n requiring k block-reversals to reach when starting from 1,2,...n.
>
> Actually I'm not yet sure that this continues as a triangle, but it seems
> likely.  There are conjectured formulas for column 2 (2, 15, 52, ...) in
> A007972.
>
> Sean.
>
> On 7 February 2018 at 05:55, Neil Sloane <njasloane at gmail.com> wrote:
>
> > Dear Seq Fans,
> >
> > We will soon reach A-number A300000.  If you see any sequences worthy of
> > this honor in the next week or two, please send me an email.
> >
> > A sequence that has already been approved can be renumbered as A300000.
> >
> > If one of you has a chance to reserve the A-numbers A300000 through
> > A300009, say, please grab them and let me know!
> >
> >
> > Best regards
> > Neil
> >
> > 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
> >
> > --
> > Seqfan Mailing list - http://list.seqfan.eu/
> >
>
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>


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