15759Re: another way to calculate primes

Expand Messages
• Dec 12, 2004
You say:
--
You have to count the "reverse" cases:

...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9
...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3
--

It seems to me you are right (more or less).
But haven't they "reverse" cases also 1x1 and 3x3 and 7 x 7 and 9 x 9?
Then we have to consider:

...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9 or 1 x 1 or 9 x 9
...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3 or 3 x 3 or 7 x 7

Gianni

______________________________________________________
----- Original Message -----
From: "Jens Kruse Andersen" <jens.k.a@...>
To: "Mazzarello Gianni" <g.mazzarello@...>
Sent: Friday, December 10, 2004 4:54 PM
Subject: Re: another way to calculate primes

Re: another way to calculate primes

----- Original Message -----
From: "Mazzarello Gianni" <g.mazzarello@...>
Sent: Friday, December 10, 2004 12:01 PM
Subject: RE: [PrimeNumbers] another way to calculate primes

> ...1 => 1 x 1 or 3 x 7 or 9 x 9
> ...3 => 1 x 3 or 7 x 9
> ...7 => 1 x 7 or 3 x 9
> ...9 => 1 x 9 or 7 x 7 or 3 x 3

You have to count the "reverse" cases:

...1 => 1 x 1 or 3 x 7 or 7 x 3 or 9 x 9
...3 => 1 x 3 or 3 x 1 or 7 x 9 or 9 x 7
...7 => 1 x 7 or 7 x 1 or 3 x 9 or 9 x 3
...9 => 1 x 9 or 9 x 1 or 7 x 7 or 3 x 3

4 cases for each digit.

--
Jens Kruse Andersen (off list)
• Show all 15 messages in this topic