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

Home > Just Math
Choose To Prime Poser (Posted on 2010-04-18) Difficulty: 3 of 5
Determine all possible values of a positive integer N ≥ 3, such that NC2 1 is a prime power.

Note: NC2 represents N choose 2.

See The Solution Submitted by K Sengupta    
No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
re(2): No Subject. No real hole in my proof. Comment 4 of 4 |
(In reply to re: No Subject by farcear)

I was thinking of (n-2) and (n+1) which if neither is 1 and they produce a prime power must be each be powers of 3.

The actual factors [1] (.5n-1)(n+1) or [2] (n-2)(.5n+.5) can differ by any value.

This does not change much since exponents grow so fast that
2*p^x+3 = p^y
and
p^x = 2*p^y - 3

Only have solutions if p=3 anyway (p cannot be 2 due to the +3 or -3)

  Posted by Jer on 2010-04-26 15:42:02

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 (2)
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