[seqfan] Re: A061421

[israel at math.ubc.ca]

Maple's "isprime" has now confirmed that 4^33478-33478-1 is (very probably) 
prime.

Robert Israel
University of British Columbia


On Dec 6 2012, israel at math.ubc.ca wrote:

>On Dec 6 2012, Georgi Guninski wrote:
>
>>On Sun, Dec 02, 2012 at 08:35:57PM +0400, юрий герасимов wrote:
>>> 
>>> Dear SegFans, If A061421 Primes of the form 2^n + n + 1 : 2, 7, 71, 
>>> 110427941548649020598956093796432407239217743554726184882600387580788973, 
>>> a(5) = 2^1884 + 1884 + 1,.., these A_____? Primes of the form 4^n - n - 
>>> 1 : 2, 13, 251, 4294967279, a(5) = ? Regards, Juri-Stepan Gerasimov.
>>>
>>
>>For computations like this, OpenPFGW is your friend:
>>
>>$egrep 'PRP|prime' /tmp/pri1.log 
>>4^1-1-1 is trivially prime!: 2
>>4^2-2-1 is trivially prime!: 13
>>4^4-4-1 is trivially prime!: 251
>>4^16-16-1 is trivially prime!: 4294967279
>>4^944-944-1 is 3-PRP! (0.0039s+0.0942s)
>>4^33478-33478-1 is 3-PRP! (8.5771s+1.3188s)
>>
>>
>>According to pari n=944 is pseudoprime.
>
>Maple's "isprime" reports 4^944-944-1 as (very probably) prime.
>This does one strong pseudo-primality test and one Lucas test.
>It's still working on 4^33478-33478-1.
>
>Robert Israel
>University of British Columbia
>
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