[seqfan] Re: A002335

Maximilian Hasler maximilian.hasler at gmail.com
Fri Feb 15 11:51:45 CET 2013


I propose as new title:
 Least y such that A038873(n) = x^2 - 2y^2, for some x.
and change offset to 1.
Would you kindly re-submit a re-indexed b-file?

Maximilian


On Fri, Feb 15, 2013 at 4:26 AM,  <israel at math.ubc.ca> wrote:
> It seems to me that the title and comment of A002335 do a poor job of
> explaining what is going on in this sequence. I could only figure it out by
> decyphering the Maple program. If p is the (n-1)'th prime for which a
> representation p = x^2 - 2 y^2 in positive integers exists, then A002335(n)
> is the least y for such a representation. Note that the representation is
> generally not unique, e.g. 17 = 5^2 - 2*2^2 = 7^2 - 2*4^2.
>
> I also don't know why the offset is 2 here, unless it has something to do
> with the fact that the first such prime is 2.
>
> Robert Israel
> University of British Columbia
>
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