[seqfan] Re: Problem

[israel at math.ubc.ca]

See sequence A257495. The b-file goes up to 7075 with no 0's, i.e. none of 
the first 7075 primes has the property.

Cheers,
Robert

On Jul 20 2020, Robert Dougherty-Bliss wrote:

>Dear Thomas,
>
>You may already be aware, but none of the first 100 primes (<= 541)
>satisfy this property.
>
>Amazingly, the earliest counterexample for p = 73 is the following integer:
>
>  
> 12525084203259602214176345117827991857573063437151079650189656689252041617399 
> 16118618976873174436648194378202145606096817433350319763375794132326993383200 
> 14217732225003163760036417965916387747831867749318699104524437655151695087826 
> 47278357731824391729532319069188907350539418959168425940169356532195426353195 
> 84257183520755212129194474630919879413057346247800071524008686049488780942766 
> 38123436651683349651892026768245860789398297612527549211852109219078820059778 
> 19346432242814374609091413789240598598335924463948419947004368457022517766034 
> 95591799870311650343246943884972083691195975663585667560716289785503524182355 
> 53897768571561351251352502155056787443177087759615376430034900988921205572639 
> 317118528079725593399200244440233458975807425711011346463660588817113315016703
>
>Robert
>
>
>Robert
>
>
>On Sun, Jul 19, 2020 at 2:28 AM Tomasz Ordowski
><tomaszordowski at gmail.com> wrote:
>>
>> Dear SeqFans!
>>
>> Let a(0) = p and a(n) = 2 a(n-1) + 1. Note that a(n) = (p+1) 2^n - 1.
>> Are there primes p such that a(n) is composite for every n > 0 ?
>>
>> Best regards,
>>
>> Thomas Ordowski
>> _______________________
>> https://en.wikipedia.org/wiki/Riesel_number
>>
>> --
>> Seqfan Mailing list - http://list.seqfan.eu/
>
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>
>