Problem 155

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viv_ban
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Problem 155

Post by viv_ban » Sat Mar 21, 2009 12:49 pm

Can anybody please confirm me if the values D(4) = 15 and D(5) = 35 are correct.
thanks in advance.

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Tommy137
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Re: problem 155

Post by Tommy137 » Sat Mar 21, 2009 12:52 pm

Yes, they are correct.
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viv_ban
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Re: problem 155

Post by viv_ban » Sat Mar 21, 2009 1:13 pm

Thanks Tommy. I really cannot understand the problem with my algorithm. Is D(10) = 2491.

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Tommy137
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Re: problem 155

Post by Tommy137 » Sat Mar 21, 2009 1:15 pm

Unfortunately, it's wrong :(
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Schwein
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Re: problem 155

Post by Schwein » Sat Aug 20, 2011 8:01 pm

I don't get it either...
Is it wrong to think, that the only new capacitor combinations are the ones from the previous, with max number of capacitors, + a series and a paralel with a new 60 microfahrad capacitor?
ex

if we have 2 2 capacitor combinations, then there will be 4 extra in the next, and 8 extra in the next and so on?

I cannot imagine how else a combination would be made, but then my D(5) = 31, and i don't see where the 4 extra comes from

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jaap
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Re: problem 155

Post by jaap » Sat Aug 20, 2011 8:52 pm

Schwein wrote:I cannot imagine how else a combination would be made, but then my D(5) = 31, and i don't see where the 4 extra comes from
Hint: 5 = 1+4 = 2+3
Remember also that we only care about the different values - some values can be made in several completely different ways, so that is another reason why it won't be a simple doubling sequence.

Schwein
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Re: problem 155

Post by Schwein » Sat Aug 20, 2011 9:56 pm

I had the part covered, that some values might be equal(turned out none of them were, when i just added one in series, and one in paralel, for each combo), the only thing i don't understand, is why that does not give me all the different combinations makeable...

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Lord_Farin
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Re: problem 155

Post by Lord_Farin » Sat Aug 20, 2011 10:10 pm

Schwein wrote:the only thing i don't understand, is why that does not give me all the different combinations makeable...
How about combining larger, 'composite' capacitors in series or parallel? (This is what hk meant above as well)
Think about $1 = \frac1{1+1}+\frac1{1+1}$.
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Schwein
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Re: problem 155

Post by Schwein » Sat Aug 20, 2011 10:21 pm

Ahhhhh, thank you were much the both of you, I see now where my logic fails ^^

Erf_Erf
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Re: problem 155

Post by Erf_Erf » Sun Jan 12, 2014 3:45 pm

It seems I can't get it right... I get the correct results for D(4) and D(5). Then D(6) = 76 and D(10) = 2147. Are these values correct?
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mpiotte
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Re: problem 155

Post by mpiotte » Sun Jan 12, 2014 6:44 pm

Erf_Erf wrote:It seems I can't get it right... I get the correct results for D(4) and D(5). Then D(6) = 76 and D(10) = 2147. Are these values correct?
No.
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Erf_Erf
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Re: problem 155

Post by Erf_Erf » Sun Jan 12, 2014 11:21 pm

I just found the annoyingly trivial and almost invisible mistake in my code, and finally got the correct answer.
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DeKlod
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Re: problem 155

Post by DeKlod » Tue Jul 09, 2019 5:00 pm

Hi all,
Could I ask for two pieces of input here:
1) D(13) is a 5-digit figure starting with a 4 and ending in an even digit - is that correct?
2) I'm using float values in C and my suspicion is that my solutions turns out wrong because of a precision issue. I've tried (long) double but the result is no more convincing. Should I try to go for the alternative of defining and manipulating fractions (as Wodehouse would have said: I've just had a look at what my mind is doing, and it turns out: it boggles!) or should I rather look for something else - my choice of value for the capacitance for example.
Cheers,
Claude

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Jochen_P
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Re: problem 155

Post by Jochen_P » Fri Jul 12, 2019 6:55 am

Claude,

to answer your first question:
D(13) is indeed a 5-digit figure but it starts with 3 and ends with an odd digit.

hth
Jochen
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DeKlod
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Re: problem 155

Post by DeKlod » Fri Jul 12, 2019 8:03 am

Right, back to the drawing board then ...
Thanks for getting back though! :-)

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