Problem 484 is still on my to-do list. I haven't looked at it in a while, but my working script includes a remark: NB. ... suggests a sieve might be ok - but for 5e15????!!! Also, I seemed to be trying to use a moebius function or Moebius' Theorem...
As I haven't managed to solve it yet, I don't suppose that is a serious spoiler!!!! Currently stuck on many of the 500s - they don't get easier, Mike On 11/07/2015 02:36, Raul Miller wrote: > I don't do project euler, I've never really gotten into it. But my > impression is that the problems are chosen to make brute force > solutions impractical. > > Here, I think I see a pattern in the relationship between >./@(_&q:) > and func (for your definition of func) and I expect that the mechanism > behind that relationship will be worth exploring. > > Good luck, > (Earlier, Jon Hough wrote:) Project Euler #484 https://projecteuler.net/problem=484is particularly troublesome. My solution is: f =: monad define T =: 5 * 10^15 ctr=:1 sum =: 0 func=:+.(+/@:(1&(*/\.))@:q:) while. ctr < T + 1 do. sum =: sum + func ctr ctr =: ctr+1 end. sum ) But on my Mac this causes a crash. (Doing a tacit one-liner with +/ gives an out of memory error). So I am at a loss how to do this in J. 10^15 seems absurdly large, so perhaps I'm missing a trick. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
