Title: | Mathematics at DEC |
Moderator: | RUSURE::EDP |
Created: | Mon Feb 03 1986 |
Last Modified: | Fri Jun 06 1997 |
Last Successful Update: | Fri Jun 06 1997 |
Number of topics: | 2083 |
Total number of notes: | 14613 |
I need to know the 5th perfect number, the one that comes after 8128. kevin
T.R | Title | User | Personal Name | Date | Lines |
---|---|---|---|---|---|
633.1 | Easy enough to check it out... | OMEGA::REILLY | Fri Dec 19 1986 18:17 | 6 | |
I don't know why, but I seem to remember that it is 33,550,336 but then again, I may be wrong..... matt (then again, it may have been the combination to a gym locker, the number sticks in my head for some reason....) | |||||
633.2 | More rigorous method | OMEGA::REILLY | Fri Dec 19 1986 18:55 | 34 | |
For what it is worth.... 8128 = 2 ^ 6 * (2 ^ 7 - 1) Since 2 ^ 7 - 1 is prime, 8128 is perfect. (This is easily proved by someone who is suitably awake.) All of the known perfect numbers are of the form 2 ^ (p - 1) * (2 ^ p - 1) where p is prime and (2 ^ p - 1) is prime. isprime(2^11 - 1); false isprime(2^13 - 1); true evalf(2^12 * (2 ^ 13 - 1)); 33550336. quit; matt btw, for grins try the above commands to MAPLE in a batch job without the quit command at the end.... i.e. the following... $ maple -q isprime(2^11 - 1); isprime(2^13 - 1); evalf(2^12 * (2 ^ 13 - 1)); convert(2^12 * (2 ^ 13 - 1), binary); | |||||
633.3 | More perfect numbers | MODEL::YARBROUGH | Mon Dec 22 1986 08:26 | 23 | |
The next few perfect numbers are 2^(k-1) * (2^k-1) for k=17 8589869056 k=19 137438691328 k=31 2305843008139952128 k=61 k=89 k=107 k=127 k=521 k=607 k=1279 k=2203 k=2281 k=3217 k=4253 k=4423 k=9689 k=9941 (5985 digits) The primes of the form 2^k-1 are the corresponding Mersenne primes. The information above is taken from Beiler's *Recreations in the Theory of Numbers*, p19. |