Search found 10 matches

by brob26
Thu Jul 15, 2021 2:22 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 761
Replies: 4
Views: 292

Re: Problem 761

This problem is driving me up the walls. I fairly easily got 4.60339314 for the circular pool (which is correct) but the same strategy gives 5.90143057 for the square pool. Can someone please confirm that the figure given in the problem for the square pool is correct. What exactly do you mean by th...
by brob26
Fri May 14, 2021 11:42 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 749
Replies: 2
Views: 319

Re: Problem 749

KeithGordon wrote: Fri May 14, 2021 10:13 pmAm I off or is the sample?
"A positive integer, $n$, is a near power sum if there exists a positive integer, $k$, such that the sum of the $k$th powers of the digits in its decimal representation is equal to either $n+1$ or $n-1$" (but not $n$ itself!)
by brob26
Thu May 06, 2021 1:55 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 756
Replies: 6
Views: 509

Re: Problem 756

Am I misunderstanding the delta Function? In a set of 20 random values for S* - S, with m = 50, n = 100, and f(k) = k, I got: -11,222,114,174,99,12,16,14,12,14,321,-10,5,16,107,118,8,183,314,107 with a mean value of 91.75 . Typically, I find 10000 random samples of (Delta|k, 100, 50) have a mean ar...
by brob26
Sun Mar 07, 2021 10:08 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 750
Replies: 3
Views: 562

Re: Problem 750

Ah, I see, basic number theory, cycle length of $ 3^k\bmod M , k=0,1,... $ should be $ M-1 $ (where M=N+1): For this M may not contain a factor 3 - then Euler's theorem tells us that $ \phi(M) $ is a upper bound (multiple) of cycle length, and $ \phi(M) = M-1 $ iff M is prime. So for G(N) to be def...
by brob26
Sun Mar 07, 2021 1:15 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 750
Replies: 3
Views: 562

Re: Problem 750

deWalk wrote: Sun Mar 07, 2021 12:05 amThe only thing I can think of, is that this suspect sequence: $ 3^n\bmod(N+1), 1\le n\le N $
may produce double values or gaps?
Nailed it
by brob26
Fri May 22, 2020 1:55 am
Forum: News, Suggestions, and FAQ
Topic: Feature suggestion
Replies: 2
Views: 1201

Re: Feature suggestion

It is fairly hidden though. It might be worth making it more visible that clicking the star sorts the thread by kudos...
by brob26
Fri May 08, 2020 1:59 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 371
Replies: 42
Views: 24299

Re: Problem 371

how is "expected to win" defined exactly? the chance of seeing a pair must be >50%? Expanding on Animus ' response, "expectation" here is defined in the statistical sense. The wikipedia page is a good place to start if you haven't encountered the concept previously. I do remembe...
by brob26
Sat Apr 11, 2020 11:29 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 711
Replies: 6
Views: 3132

Re: Problem 711

"First, they agree on a positive integer n, and they begin by writing its binary representation on a blackboard."

So for n = 1, they start by writing "1". Then it's Oscar's turn, but his only option is to write another "1", leaving an even number of 1s on the board.
by brob26
Tue Jul 30, 2019 12:46 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 618
Replies: 8
Views: 4825

Re: Problem 618

Your answer for $S(21)$ is wrong- the correct value is roughly a quarter of yours. If it helps diagnose the bug, there are $30$ distinct numbers which have a prime factor sum of $21$; the lowest is $38$, and the largest $2187$.
by brob26
Sun Jan 20, 2019 8:19 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 652
Replies: 1
Views: 1257

Re: Problem 652

Can we assume this conjecture for the given N=10^18? If making this assumption leads you to a different answer, then you've disproved the four exponentials conjecture! So either it's fine to assume the conjecture holds for larger N, or you settle a currently unsolved problem in number theory. Eithe...