[seqfan] Re: A132870 : a Mathematica line
Marc LeBrun
mlb at well.com
Mon Nov 20 20:19:54 CET 2017
Wouldn't it be nicer to have two sequences, a numerator and a denominator?
> On Nov 20, 2017, at 10:44 AM, Neil Sloane <njasloane at gmail.com> wrote:
>
> Since the triangle is integral for a long time, I think it is enough to
> leave the entry the way it is, but to make it clear in the comments that
> this stops being integral beyond a certain point.
>
> There is a famous recurrence (discussed by Lenstra) which is integral for
> 48 or so terms but then isn;'t, and we handled that in the same way. We
> pretend it is integral, but add a warning that it really isn't.
> And we stop the b-file before we hit the rocks.
>
>
> 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 Mon, Nov 20, 2017 at 12:47 PM, Paul Hanna <pauldhanna.math at gmail.com>
> wrote:
>
>> Wouter,
>> Thanks for verifying the fractional elements.
>> "Bummer" is right ...
>> I'll ask Neil what to do with the non-integral triangle.
>> Thank you!
>> Paul
>>
>> On Sat, Nov 18, 2017 at 11:50 AM, Wouter Meeussen <
>> wouter.meeussen at telenet.be> wrote:
>>
>>> pt = {{1}}; Table[rhs = CoefficientList[(k^2 + x)^k, x];
>>> qt = Join[pt, {vars = Array[Subscript[a, #] &, k + 1]}];
>>> b = MatrixPower[PadRight[qt], k] ;
>>> {out} = vars /. Solve[Thread[Reverse[Last[b]] == Reverse[rhs]], vars];
>>> pt = Join[pt, {out}]; out, {k, 20}]
>>>
>>>
>>> not the fastest of codes : the first 20 rows take 43 seconds on my old
>>> machine.
>>>
>>>
>>> W.
>>>
>>> --
>>> Seqfan Mailing list - http://list.seqfan.eu/
>>>
>>
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>> Seqfan Mailing list - http://list.seqfan.eu/
>>
>
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