[seqfan] Re: Suggestions for A300000 ?

Sean A. Irvine sairvin at gmail.com
Fri Feb 23 01:56:40 CET 2018


A299968.


On 23 February 2018 at 13:17, Neil Sloane <njasloane at gmail.com> wrote:

> 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
> > >
> > > --
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> > >
> >
> > --
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> >
>
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