At 4:31 PM +0200 4/28/04, Otto Spaniol wrote:
Dear all,
until now a percect number of delegates have confirmed their attendance, namely 28 (see annex).
Comment: A number is called perfect if the sum of its integer factors (excluding itself, of course) is equal to the number. 28 is one of the few perfect numbers since 28 = 1 + 2 + 4 + 7 + 14. Other perfect numbers are 6 and 496. There are not very many of them and I don't really know whether there is another one. However, it is unknown (as far as I know) whether the the total number of them is finite or infinite.
Otto,
If we reach 496 we will indeed have the largest TC6 attendance ever! And the next perfect number is 8128, which is even further out of reach.
It is known that the only even perfect numbers are the numbers 2^(p-1)(2^p - 1), where p is a prime such that 2^p - 1 is also prime. Mathematicians think that the number of Mersenne primes (and therefore the number of even perfect numbers) is "probably" infinite, but there is no proof. There is also no proof that there is not an odd perfect number, but it is known that if there is one, it is very large (more than 300 decimal digits) - which is too bad, because the best number for TC6 would be both perfect and odd :-)
- Lyman