[seqfan] Re: (3^n+1)/2 is prime, A171381

[Max Alekseyev]

These and some other factors are given in Björn & Riesel paper:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.108.8250&rep=rep1&type=pdf
and the follow-up at
http://www1.uni-hamburg.de/RRZ/W.Keller/GFNfacs.html

Regards,
Max


On Mon, Jun 14, 2010 at 12:57 AM, Maximilian Hasler
<maximilian.hasler at gmail.com> wrote:
> On Sun, Jun 13, 2010 at 7:31 AM, Georgi Guninski <guninski at guninski.com> wrote:
>> On Sun, Jun 13, 2010 at 01:24:58AM -0400, N. J. A. Sloane wrote:
>>> %E A171381 Incorrect terms a(7)-a(15) deleted Jun 12 2010 by Jon Schoenfield
>>> (or in other words, 0,1,2,4,5,6,>=15)
>>> Can anyone find the next term?
>>
>> 2^{15,16,17,18} are not in the sequence
>
> More terms not in the sequence, because
> (3^(2^m)+1)/2  is divisible by  1+2^(m+1)*q :
>
> [m,q] =
> [3, 1]
> [7, 1]
> [8, 24]
> [10, 29]
> [11, 193]
> [15, 1]
> [19, 13]
> [21, 37]
> [26, 24]
> [28, 23]
> [29, 72]
> [31, 1080]
> [32, 24]
> [34, 1469]
> [36, 6630]
> [38, 12]
> [39, 42]
> [44, 443]
> [45, 228]
> [49, 7]
> [51, 198]
> [54, 5]
> [56, 2460]
> [60, 3810]
> [61, 18]
> [63, 12]
> [64, 36]
> [72, 804]
>
> Maximilian
>
>
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