Problem 386

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Djinx
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Problem 386

Post by Djinx »

I understand it is perhaps too early to ask for help in this problem, but i would appreciate if someone who solved it comment on my values:

EDIT: Values removed, at least for the time.
Last edited by Djinx on Mon May 28, 2012 4:54 pm, edited 1 time in total.
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hk
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Re: Problem 386

Post by hk »

Djinx wrote:I understand it is perhaps too early to ask for help in this problem,
Yes it is by some weeks.
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Djinx
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Re: Problem 386

Post by Djinx »

hk wrote:
Djinx wrote:I understand it is perhaps too early to ask for help in this problem,
Yes it is by some weeks.
Okay, then. Should I remove the post altogether?
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hk
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Re: Problem 386

Post by hk »

I leave that to your courtesy.
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Djinx
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Re: Problem 386

Post by Djinx »

Considering that the number of solvers has already crossed the 100 mark, and the peculiarity of problems I am facing, I feel justified in asking for help one more time.

I could find a formula for the answer, and it does work perfectly fine against values I found against those by brute force for n=100, 1000, 10000. I also verified my code for some random values under 10^8. However, the final answer is still not accepted.

EDIT: It all turned out to be an overflow error :lol:. I apologize for my impatience.
Last edited by Djinx on Thu May 31, 2012 1:27 am, edited 1 time in total.
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hk
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Re: Problem 386

Post by hk »

Djinx wrote: I could find a formula for the answer, and it does work perfectly fine against values I found against those by brute force for n=100, 1000, 10000. I also verified my code for some random values under 10^8. However, the final answer is still not accepted.
That's a hallmark for overflow problems.
So if you could be so kind as to remove all information about the problem itself, i.e. your spelled out assumptions that would be great.
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impulse
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Joined: Sat Jun 02, 2012 9:56 am

Re: Problem 386

Post by impulse »

hk wrote: That's a hallmark for overflow problems.
Hi, I just want to know whether the solution is under the limit of 32 bits.
And can anyone provide a sample case please.
LarryBlake
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Re: Problem 386

Post by LarryBlake »

Can someone confirm if the maximal antichain for 120120 = 30?
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thundre
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Re: Problem 386

Post by thundre »

Yes, the sum fits in 32 bits.
LarryBlake wrote:Can someone confirm if the maximal antichain for 120120 = 30?
Expand
No, 30 is too many. If you look at your list of 30 numbers, there will be one which divides another.
edit: Hidden because it was WRONG.
Last edited by thundre on Thu Feb 07, 2013 1:43 pm, edited 1 time in total.
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LarryBlake
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Re: Problem 386

Post by LarryBlake »

Okay, thanks.
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LarryBlake
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Re: Problem 386

Post by LarryBlake »

Thundre, I just verified that my antichain of 30 elements contains no divisible numbers. Did you mean that 29 is the highest index starting at zero?

In any case, is it safe to say that there is no larger antichain for N(120120)?
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thundre
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Re: Problem 386

Post by thundre »

LarryBlake wrote:Thundre, I just verified that my antichain of 30 elements contains no divisible numbers. Did you mean that 29 is the highest index starting at zero?

In any case, is it safe to say that there is no larger antichain for N(120120)?
30 is correct for 120120. I typed in 210210, which has a shorter maximal antichain.

I apologize for the bad advice.
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LarryBlake
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Re: Problem 386

Post by LarryBlake »

No problem, thanks for the reply.

Guess I won't be in the first 100 solvers for this one. :lol:
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tinnderbox
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Problem 386

Post by tinnderbox »

Hi,
since this problem is now nearly four years old and solved by over 400 the text is apparently clear enough.
Still, I was initially bemused for a few moments by the problem text.

The first line says
Let ...S(n) be the set of factors of n.
Then, a few lines lower:
For example: S(30) = {1, 2, 3, 5, 6, 10, 15, 30} \

Are the factors of 30 not {2,3,5} ?
Shouldn't the first line say: divisors ?
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jaap
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Re: Problem 386

Post by jaap »

tinnderbox wrote:The first line says
Let ...S(n) be the set of factors of n.
Then, a few lines lower:
For example: S(30) = {1, 2, 3, 5, 6, 10, 15, 30} \

Are the factors of 30 not {2,3,5} ?
Shouldn't the first line say: divisors ?
Factor and Divisor mean the same thing in this context. {2,3,5} are the prime factors or prime divisors.
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