[seqfan] Re: easy and bref
franktaw at netscape.net
franktaw at netscape.net
Fri Sep 30 19:07:25 CEST 2011
Well, consider A000043: Mersenne primes (p with 2^p-1 prime).
Currently, we don't know any very efficient way of calculating these.
(Better than primality testing for other numbers of the magnitude 2^p,
but still very expensive as a function of p.) However, no one has
proved that there isn't an efficient way to compute these. (The list
might even be finite, in which case there is a very efficient
calculation.)
Franklin T. Adams-Watters
-----Original Message-----
From: Charles Greathouse <charles.greathouse at case.edu>
> Interesting. My understanding of "hard" was just the opposite: that it
> should be used when it is known that calculating more terms is hard,
but not
> when there might be an easier way to make the calculation, but none
such is
> known.
I'm not sure when that would ever apply. Would you give some examples?
Charles Greathouse
Analyst/Programmer
Case Western Reserve University
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