# [seqfan] Re: A139414

Harry J. Smith hjsmithh at sbcglobal.net
Wed Jan 28 21:58:11 CET 2009

I vote for defining a(79)=0.

76 13381
77 14087
78 14561
79 0
80 15541
81 15791
82 16553

I will add some comments to the sequence A139414 and submit a b-file.

-Harry

> -----Original Message-----
> From: seqfan-bounces at list.seqfan.eu [mailto:seqfan-bounces at list.seqfan.eu]
On
> Behalf Of Ray Chandler
> Sent: Tuesday, January 27, 2009 10:25 AM
> To: 'Sequence Fanatics Discussion list'
> Subject: [seqfan] Re: A139414
>
> >  i tried to understand A139414
> >  (and then submit comment etc.) but failed, see:
> > http://zak08.livejournal.com/5346.html
> >
> > Hope someone with better English/math
> > (better than Roger?! ...i doubt...)
> > may wish to submit a proper comment/editing,
> >
> > thx, zak
>
> Looking at the code included with the sequence, the polynomials are tested
in a cycle
> beginning with a[1 + Mod[x,4]],
> i.e. when x==0 mod 4, they are tested in order a1,a2,a3,a4; when x==1 mod
4, they are
> tested in the order a2,a3,a4,a1,
prime to
> choose if there are multiples.
>
> The second question regarding what to do if none of the polynomials
produces a
> prime, cannot be answered so easily.
> Since the examples stop with x=78 and the first occurrence of no prime
occurs at x=79
> , it is not clear what the
> author's intent was.
> The sequence could simply stop at that point ("fin") or we could add "or
zero if no
> prime exists" to definition and
> continue.
> A third option is to just drop terms where there is no prime, but that
messes up the
> index.
> Ray
>
>
>
>
>
>
>
>
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