[seqfan] Re: Primes of the form kn+1
Robert Gerbicz
robert.gerbicz at gmail.com
Thu Dec 17 19:00:07 CET 2009
2009/12/17 Michael Porter <ic_designer at verizon.net>
> Is it true that for every positive integer n, there is a prime of the form
> kn+1 with 1<=k<=n?
>
> I submitted the following PARI program for sequence A089727:
> A089727(n) = {local(k);k=n;while(!isprime(n*k+1),k--);n*k+1}
> and then I started wondering if the while loop would always terminate.
>
> Thanks,
> Michael
>
>
>
>
> _______________________________________________
>
> Seqfan Mailing list - http://list.seqfan.eu/
>
That's very probably because the expected smallest k for which k*n+1 is
prime (in average) is about eulerphi(n)*log(n)/n.
More information about the SeqFan
mailing list