Seriously disagreement

Peter Pein petsie at
Wed Sep 3 00:52:33 CEST 2008

The page starts (after a tble of contents) wit a table of x (propably upper
bound of x) in the left column and the right column has got the title "Primes".

Near the bottom (numbered "4.") the first entry says that 1 is prime.

These are unmisunterstandable (is there such an word in english language?)
statements which are wrong. There is enough space to write "prime divisors" if
one wants. But the author wrote "Primes". Therefore it is nonsense.

Sorry for my ignorance but I do not want to have to _guess_ or _search_for_
the meaning of words  when reading websites concerning mathematics.


franktaw at schrieb:
> A closer look at this web page shows that this is counting the number of
> distinct prime divisors of numbers of the form 2x^2-1 for x <= 10^n, not
> the number of primes.
> Note that there can be at most one prime divisor of 2x^2-1 that does
> not divide 2y^2-1 for some y < x.  Every prime divisor p except possibly
> one must be < 2x (in fact, p < sqrt(2) x), at which point p divides
> 2 |x-p|^2 - 1.
> Franklin T. Adams-Watters
> -----Original Message-----
> From: Artur <grafix at>
> Dear Seqfans, 
> On www page 
> we can read that number of primes of the form 2x^2-1 for x equal or less
> than 10^n is 
> 8, 84, 815, 7922, 77250, 759077, 7492588, 74198995, 736401956, 
> 7319543971, 72834161467 
> ...

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