mersenneforum.org Calculating perfect numbers in Pascal
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 2008-06-11, 06:30 #1 Elhueno   2×7×103 Posts Calculating perfect numbers in Pascal Hi all i was just wondering if anyone here has ever tried to calculate perfect numbers from scratch in Bloodshed softwares Dev-Pascal. i have been tasked to do this for a college teacher. any help would be appreciated. and the sooner the better.
2008-06-11, 13:01   #2
R.D. Silverman

Nov 2003

11101001001002 Posts

Quote:
 Originally Posted by Elhueno Hi all i was just wondering if anyone here has ever tried to calculate perfect numbers from scratch in Bloodshed softwares Dev-Pascal. i have been tasked to do this for a college teacher. any help would be appreciated. and the sooner the better.
What do you mean by "calculate perfect numbers"? Do you mean

"write a program that will find p such that 2^p-1 is prime?"

Once you have such p, then a perfect number is just (2^p-1) * 2^(p-1)
Hint: this has already been done.

Or do you mean

"given a list of such p, compute 2^(p-1) * (2^p -1)"??

If so, you must again specify what you mean by "compute".

Do you mean "calculate the decimal representation"? or "calculate the
hex representation"? or "calculate the binary representation"?? [the latter
two are trivial].

2008-06-11, 13:22   #3
Mini-Geek
Account Deleted

"Tim Sorbera"
Aug 2006
San Antonio, TX USA

17·251 Posts

Quote:
 Originally Posted by R.D. Silverman What do you mean by "calculate perfect numbers"? Do you mean "write a program that will find p such that 2^p-1 is prime?" Once you have such p, then a perfect number is just (2^p-1) * 2^(p-1) Hint: this has already been done. Or do you mean "given a list of such p, compute 2^(p-1) * (2^p -1)"?? If so, you must again specify what you mean by "compute". Do you mean "calculate the decimal representation"? or "calculate the hex representation"? or "calculate the binary representation"?? [the latter two are trivial].
I'd assume he meant a program that finds perfect numbers by factoring numbers, adding their factors, then seeing if those two are equal. A better way to calculate, as you suggested, would be to find Mersenne primes (preferably by LL test) and know the perfect numbers by that.
I think a better, revised question would be how to write the LL test in Pascal.

 2008-06-12, 13:00 #4 Housemouse     Feb 2008 2016 Posts Any program to search for an odd perfect number, if any exist?
2008-06-12, 13:08   #5
bsquared

"Ben"
Feb 2007

3,361 Posts

Quote:
 Originally Posted by Housemouse Any program to search for an odd perfect number, if any exist?
www.oddperfect.org

 2008-06-12, 16:37 #6 philmoore     "Phil" Sep 2002 Tracktown, U.S.A. 2×13×43 Posts My impression of the original poster's request was that this was an assignment in programming rather than a math project. My guess is that the teacher wanted a program, which for each integer input n, computed the sum of proper divisors of n to see if it is equal to n, perhaps contained in a loop incrementing n. This can be done in a very simple-minded (and inefficient) way, or one could apply a bit of math to make the search more efficient. Perhaps the original poster should clarify what is really wanted.

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