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

[Georgi Guninski]

On Mon, Jun 14, 2010 at 12:25:22PM -0400, N. J. A. Sloane wrote:
> I'm trying to keep
> all three entries - A093625, A138083, A171381 up to date
> (tricky because there has been a lot of email
> about them)
> 
> the next term is >= 2^21 (Don Reble from 2004)
>

looks like Max killed 2^21 as per his mail:

? q=21;p=(37*2^(q+1)+1)
%154 = 155189249
? lift(Mod(3,p)^(2^q)+1)
%155 = 0
? zz=(3^(2^q)+1)/2;zz%p
%156 = 0
? round(log(zz)/log(10))
%157 = 1000595