[seqfan] Re: Comment about A002822

[israel at math.ubc.ca]

I agree that it is not efficient, but neither is Wilson's theorem.
That shouldn't disqualify it from being mentioned in a comment.

Cheers,
Robert

On May 24 2019, Heinz, Alois wrote:

>
>This is not efficient:
>
>See the for-loop "from 1 to k"
>
>Please do not add this as a comment.
>
>Best regards,
>
>Alois
>
>Am 24.05.2019 um 11:29 schrieb nando:
>> Hi SeqFans,
>>
>> I know about an algorithm for testing whether an integer n belongs to
>> the A002822 sequence (Numbers n such that 6n-1, 6n+1 are twin primes).
>> The interesting part (at least for me) is that this algorithm involves
>> no primality tests whatsoever.
>>
>> For n >= 4
>> * compute k = floor((1+sqrt(1+6n))/6)
>> * n is a member of A002822 iff neither (6j-1) nor (6j+1) divide
>> (n^2-j^2) for all j from 1 to k
>>
>> For n < 4, the above k turns out to be 0, so there are no filters and
>> the test is passed by default.
>>
>> I've never seen this algorithm mentioned anywhere, so I'm looking for
>> feedback from the list subscribers as to whether or not this could
>> possibly be a worthy addition to the comments of that sequence.
>>
>> Thanks.
>> -- Nando
>>
>> --
>> Seqfan Mailing list - http://list.seqfan.eu/
>
>
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