Yes. Use a sieve. Don On May 17, 11:36 pm, wujin chen <wujinchen...@gmail.com> wrote: > @Daveļ¼ thanks for your reply. > i know that, i can only check from 6*n - 1 and 6*n + 1.. > assume that, n=10000 , 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 some math principle to solve this problem easily? > > 2011/5/18 Dave <dave_and_da...@juno.com> > > > @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 chen <wujinchen...@gmail.com> wrote: > > > given a number n, compute the smallest prime that is bigger than n. > > > for example, n=8, then the smallest prime that bigger than 8 is 11. > > > > i wonder whether there is an effective way, rather than check every > > number > > > bigger than n one by one. > > > > thanks. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Algorithm Geeks" group. > > To post to this group, send email to algogeeks@googlegroups.com. > > To unsubscribe from this group, send email to > > algogeeks+unsubscr...@googlegroups.com. > > For more options, visit this group at > >http://groups.google.com/group/algogeeks?hl=en. > >
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