--- In

primenumbers@yahoogroups.com, Jack Brennen <jfb@...> wrote:

>

> Where did you get the numbers, I'm wondering...

>

> One thing I noticed was that for each of your N, sigma(N) is

> divisible by 7 and 19-smooth (no prime divisors > 19).

>

> However, there are probably thousands of other numbers less

> than 6158856 which have sigma(N) very smooth and divisible by 7,

> so there must be more to it. Still, I have to think that whatever

> these numbers have in common somehow ties in with the smoothness

> of sigma(N); the divisibility by 7 may be a coincidence.

>

In addition, the five numbers are each one less than a prime.

>

>

> On 1/17/2011 12:32 PM, Di Maria Giovanni wrote:

> > Hi

> > Does it exist a formula to generate the following numbers?

> >

> > 36

> > 540

> > 39508

> > 667332

> > 6158856

> >

> > Regards

> > Giovanni

> >

> >

> >

> >

> >

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>