Mini-challenge: First Prime of form 403333...
|
11-14-2016, 08:20 PM
Post: #14
|
|||
|
|||
RE: Mini-challenge: First Prime of form 403333...
Hi, Thomas: (11-14-2016 09:02 AM)Thomas Ritschel Wrote: Thanks for the detailed analysis! You're welcome, but I wouldn't call my post an analysis, more like a few observations I made on the go while solving the challenge. Quote:[...]every second number of the sequence 403333... (those with an even number of digits) has algebraic factors: Interesting. Did you notice this pattern yourself or did you read about it someplace ? In that case, I would appreciate a link to it. Quote:Thus, in general, one can skip the even exponents; in your case the odd indices. Together with the "mod 6" congruences this reduces to testing only the case index = 4 mod 6. Great. This way, instead of having to check 483 candidates, only about 60-70 will need to be checked out, an 800% speed up. Thanks a lot for posting those really interesting facts, a real textbook example of how a little analysis can do much better than relying in just pure brute force. Regards. V. All My Articles & other Materials here: Valentin Albillo's HP Collection |
|||
« Next Oldest | Next Newest »
|
User(s) browsing this thread: 1 Guest(s)