All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers
Composite? Yes. (Posted on 2010-08-24) Difficulty: 3 of 5
Prove that (258+1)/5 is a composite number.

No Solution Yet Submitted by Ady TZIDON    
No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
Hints/Tips another approach | Comment 2 of 3 |

The factorisation 2^(4n+2)+1 = [2^(2n+1)-2^(n+1)+1]*[(2^2n+1)+2^(n+1)+1] suggests to me that not only is the expression  divisible by 5, but also that every prime factor of the expression is itself a prime of the form 4k+1, or a power of such a number.


  Posted by broll on 2010-08-25 07:23:41
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (7)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information