[seqfan] Re: No right isosceles triangles in a square grid

Neil Sloane njasloane at gmail.com
Sat Apr 23 00:08:00 CEST 2016


Rob, Yes, you are right! I missed that. But I still expect that the answer
will be 2n-2 for n>1,
and so this sequence (A271907) will soon be replaced by a comment in a271906

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 Fri, Apr 22, 2016 at 5:38 PM, Rob Pratt <Rob.Pratt at sas.com> wrote:

> This comment seems wrong;
> " By using two edges of the grid minus their intersection we get a(n) >=
> 2n-2. - N. J. A. Sloane, Apr 22 2016"
>
> For example, the cells (1,5), (4,1), and (9,1) lie in such a set but form
> an isosceles triangle.
>
> -----Original Message-----
> From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Neil
> Sloane
> Sent: Friday, April 22, 2016 2:50 PM
> To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> Subject: [seqfan] Re: No right isosceles triangles in a square grid
>
> If you did not find any clever solutions for n <= 11, I bet we have  a(n) =
> 2n-2 for all n>1.
>
> 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 Fri, Apr 22, 2016 at 1:35 PM, Giovanni Resta <g.resta at iit.cnr.it>
> wrote:
>
> > Il 22/04/2016 17:34, Neil Sloane ha scritto:
> >
> >> 1, 2, 4, 6, 8, 10, 12, 14, 14, 16, 20
> >>>
> >> Could there be a typo? Did you mean to say
> >>
> > Yes, sorry. I did make a mess merging results from Mathematica,
> > lp_solve and cplex.
> > It is 1,2,4,6,8,10,12,14,16,18 (I'm checking again a(11)=20 because I
> > deleted the result),  i.e.,  it seems simply a(1)=1 and a(n)=2n-2 up
> > to a(10).
> >
> > I'm going to check again the results when I prepare the pictures.
> > Sorry for the error,
> >
> > Giovanni
> >
> > --
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> >
>
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