## Search found 25 matches

- Wed Jun 05, 2019 12:23 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 610
- Replies:
**16** - Views:
**4136**

### Re: Problem 610

Hello. I solved 610 last night, and DJohn's post was helpful in formulating my solution. To be clear, in answering the problem, CMD is indeed considered invalid, as well as many of the other examples in the thread for problem 89 . However, I'm not sure that this is definitively ruled out by the Abou...

- Fri Apr 26, 2019 1:48 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 285
- Replies:
**17** - Views:
**9217**

### Re: Problem 285

I have just completed this problem and I can confirm that these are the correct values. I'm not sure what is going on in the rest of this thread.

- Tue Mar 05, 2019 10:57 pm
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 641
- Replies:
**5** - Views:
**2103**

### Re: Problem 641

*A Long Row of Dice*. No kidding. By my calculations, that many dice in a row is many orders of magnitude longer than the length of the observable universe.

- Wed Nov 14, 2018 9:45 am
- Forum: Clarifications on Project Euler Problems
- Topic: Problem 521
- Replies:
**9** - Views:
**3813**

### 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:
**4** - Views:
**7471**

### 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:
**14** - Views:
**8085**

### 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:
**14** - Views:
**8085**

### 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:
**13** - Views:
**8989**

### 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:
**1959**

- Mon Sep 10, 2018 11:34 pm
- Forum: News, Suggestions, and FAQ
- Topic: ProjectEuler.net "Level"
- Replies:
**3** - Views:
**1959**

### 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:
**5366**

### 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:
**14** - Views:
**3662**

### 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:
**3836**

### 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:
**1574**

### 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:
**6647**

### 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:
**1920**

### 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:
**4** - Views:
**7471**

### 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:
**4** - Views:
**7471**

### 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:
**754**

### 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:
**754**

### 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...