http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
On Thu, May 19, 2011 at 1:47 AM, Don dondod...@gmail.com wrote:
Yes. Use a sieve.
Don
On May 17, 11:36 pm, wujin chen wujinchen...@gmail.com wrote:
@Dave， thanks for your reply.
i know that, i can only check from 6*n - 1 and 6*n + 1..
Yes. Use a sieve.
Don
On May 17, 11:36 pm, wujin chen wujinchen...@gmail.com wrote:
@Dave， thanks for your reply.
i know that, i can only check from 6*n - 1 and 6*n + 1..
assume that, n=1 , and we begin from k=1667, the number needed to check
is 10001,10003
but to determin 10001 is
@Wujin: Well, obviously, you don't have to check _every_ number one-by-
one. If n 1, you can ignore every even number. Furthermore, if n
3, you can ignore every odd multiple of 3. That means that you need to
check only numbers of the form 6*n - 1 and 6*n + 1.
Dave
On May 17, 9:09 pm, wujin
@Dave， thanks for your reply.
i know that, i can only check from 6*n - 1 and 6*n + 1..
assume that, n=1 , and we begin from k=1667, the number needed to check
is 10001,10003
but to determin 10001 is prime or not costs a lot, right?
when the n is huge, it will be not feasible.
is there
