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

Georgi Guninski guninski at guninski.com
Sun Jun 13 13:31:17 CEST 2010


On Sun, Jun 13, 2010 at 01:24:58AM -0400, N. J. A. Sloane wrote:
> %E A171381 Edited by N. J. A. Sloane, Dec 09 2009
> %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?  (Otherwise it is awfully close to the
> powers of 2)
>

2^{15,16,17,18} are not in the sequence

user interrupt after 2h, 28mn, 32,890 ms.

(3^(2^15)+1)/2 is divisible by  2^(2^4)+1





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