# [seqfan] Re: A139414

David Wilson dwilson at gambitcomm.com
Thu Jan 29 21:56:05 CET 2009

```This is a sequence I would personally vote off the island. It looks
contrived, and nothing in the sequence gives me the slightest reason to
care about it. Is there some reason I should be interested?

Harry J. Smith wrote:
> 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,
>> etc.  That answers the question already posted in comments about which
>>
> 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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>>
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>>
>
>
>
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>
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>

```

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