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

[Maximilian Hasler]

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