## Search found 22 matches

- Wed Nov 14, 2018 9:45 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 521
- Replies:
**9** - Views:
**2313**

### Re: Problem 521

There are plenty of test solutions in these forums... maybe the rule needs to be clarified?

- Fri Nov 02, 2018 11:05 am
- Forum: Number Theory
- Topic: Project Euler Factoring Challenge
- Replies:
**3** - Views:
**1829**

### Re: Project Euler Factoring Challenge

I thought more people would get into this, but anyway I factored the 80 digit number with the quadratic sieve.

I started coding the number field sieve algorithm but have gotten stuck on the square root problem.

I started coding the number field sieve algorithm but have gotten stuck on the square root problem.

- Thu Oct 18, 2018 12:24 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 272
- Replies:
**12** - Views:
**3929**

### Re: Problem 272

For future solvers: if you end up getting the correct wrong answer above, you are about 95% there, and understand the problem well enough to identify the issue and solve it.

- Wed Oct 17, 2018 7:44 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 272
- Replies:
**12** - Views:
**3929**

### Re: Problem 272

Could anyone confirm that: 1) there are 663 positive results for n <= 3 * 10^7 for a total of 13166591472. 2) there are 29454 positive results for n <= 3 * 10^8. Thanks. Strangely enough, I get these wrong results as well EDIT: found my issue. Though I probably can't say too much about it. OK I hav...

- Tue Sep 11, 2018 10:31 am
- Forum: Recreational
- Topic: Suggest me a book
- Replies:
**10** - Views:
**2272**

### Re: Suggest me a book

My "go to" book is "Elementary Number Theory" by David M. Burton. I don't even know where I got it from but the main thing I like about it is that the mathematical detail is interspersed with interesting historical details. Both "Prime Numbers: A Computational Perspective", Pomerance & Crandall, and...

- Tue Sep 11, 2018 10:21 am
- Forum: News, Suggestions, and FAQ
- Topic: ProjectEuler.net "Level"
- Replies:
**3** - Views:
**861**

- Mon Sep 10, 2018 11:34 pm
- Forum: News, Suggestions, and FAQ
- Topic: ProjectEuler.net "Level"
- Replies:
**3** - Views:
**861**

### Re: ProjectEuler.net "Level"

Just Curious -- How is it that some posts include the author's Project Euler (Problems solved) "Level" and most do not? I tried looking at my UserControlPanel/Profile/EditSignature and elsewhere but this is yet another Project Euler riddle I can't solve! Just type the following into your signature ...

- Tue Sep 04, 2018 9:17 am
- Forum: Number Theory
- Topic: An Infinite Prime Number Generator
- Replies:
**5** - Views:
**1189**

### Re: An Infinite Prime Number Generator

I did something similar to this when I was learning about the many applications of sieving. At the time I could fit a sieve of size around 10^8 in memory, so sieving just odd numbers gives a quick algo for primes up to 2x10^8. Running two sieves, residue 1 and 5 mod 6 boosts performance by a factor ...

- Thu Dec 28, 2017 11:32 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 250
- Replies:
**12** - Views:
**2482**

### Re: Problem 250

I just solved 249 and 250. While 249 is probably easier to understand, 250 is (can be?!) definitely the easier problem computationally!

- Fri Dec 15, 2017 9:46 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 287
- Replies:
**14** - Views:
**3323**

### Re: Problem 287

Hmm... It seems like each encoding can refer to different images. For example, 011101010 could refer to both: ox xx as well as ooxx ooxx xxxx xxxx (here o represents white and x represents black squares). The larger image could be enforced by splitting one of the 2x2 squares but then that encoding c...

- Fri Nov 17, 2017 8:52 am
- Forum: News, Suggestions, and FAQ
- Topic: Solution thread
- Replies:
**8** - Views:
**789**

### Re: Solution thread

Personally I think the solutions forums are the best part of PE (apart from the problems of course!). One of the most exciting things on this site is seeing a variety of approaches to solving any particular problem; some problems really only have one solution but many problems have many different wa...

- Tue Nov 14, 2017 11:00 pm
- Forum: Recreational
- Topic: Solving PE problems multiple times.
- Replies:
**7** - Views:
**1956**

### Re: Solving PE problems multiple times.

Haha! I have wasted enough time solving problems once to consider starting again!

- Sat Jun 17, 2017 10:40 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 606
- Replies:
**8** - Views:
**1598**

### Re: Problem 606

I am in a similar position with this problem. I've worked out the formula for the answer, and even a semi-smart way of calculating it without generating massive amounts of primes, but my estimate for the calculation time needed is still ~1000 hrs. My rule of thumb is that if I find myself needing to...

- Sat Jun 03, 2017 6:22 am
- Forum: Number Theory
- Topic: Project Euler Factoring Challenge
- Replies:
**3** - Views:
**1829**

### Re: Project Euler Factoring Challenge

Here are some 1-minute benchmarks from different methods I've tried: Trial factoring can factor 18 digits in less than one minute, but quickly becomes infeasible. The continued fraction method is a good way to get into the more complex methods. With CF I can factor the 34-digit number in 1 minute. I...

- Thu Mar 23, 2017 7:43 am
- Forum: Number Theory
- Topic: Project Euler Factoring Challenge
- Replies:
**3** - Views:
**1829**

### Project Euler Factoring Challenge

As far as I'm aware there's no problems in Project Euler that require us to factor really big numbers. And yet, some of the more recent factorisation algorithms are really fascinating! So here it is - The Project Euler Factoring Challenge: pefc=[6, 21, 781, 1081, 31747, 312017, 3180883, 53011019, 42...

- Tue Feb 14, 2017 11:14 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 590
- Replies:
**2** - Views:
**520**

### Re: Problem 590

OK thanks sjhillier. At least I'm on the right track now (I think!).

It seems like 'the least common multiple of the integers in the set' is still somewhat ambiguous for the same reason, until the lcm of three numbers is defined.

It seems like 'the least common multiple of the integers in the set' is still somewhat ambiguous for the same reason, until the lcm of three numbers is defined.

- Tue Feb 14, 2017 10:11 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 590
- Replies:
**2** - Views:
**520**

### Problem 590

I haven't been able to find a satisfactory definition of the lcm of a set in my usual references. Just to be clear, I assume that lcm(a,b,c) = lcm(a,lcm(b,c)), so that lcm(2,3,5) = 30. An alternative definition (probably wrong) of lcm of a set might be the maximum lcm of elements taken pair-wise, in...

- Wed May 18, 2016 1:48 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 144
- Replies:
**19** - Views:
**6006**

### Re: Problem 144

Wouldn't it be great if just once there was a trick question as alluded to here with the answer equal to 0?mpiotte wrote:The light beam enters through the gap at x ~ 0.0071 (-0.01 <= 0.0071 <= 0.01).grump wrote:Doesn't the laser beam get reflected off the top before it ever makes it into the ellipse?

- Thu Mar 03, 2016 7:06 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 516
- Replies:
**5** - Views:
**2201**

### Re: Problem 516

I'm getting close to a solution on this.rakeshp wrote:is

S(1000000)=2236471777

S(1000000000)=964002218

correct?

For those who might use these numbers to check their method, it might save some time to point out that these two answers are actually mod 2^32, rather than S(L) itself.

- Tue Aug 04, 2015 10:04 am
- Forum: News, Suggestions, and FAQ
- Topic: PE has been hacked (02/08/2015 00:42 CEST)
- Replies:
**36** - Views:
**8567**

### Re: PE has been hacked (02/08/2015 00:42 CEST)

Like the rest of you, I'm struggling to understand the logic of hacking PE.

Why not demonstrate how good you are at computers by... I don't know... maybe solving as many PE problems as possible?

Why not demonstrate how good you are at computers by... I don't know... maybe solving as many PE problems as possible?