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

Home > Numbers
Does it continue? 5: powers of 2 (Posted on 2017-09-24) Difficulty: 3 of 5
Before trying the problem "note your opinion as to whether the observed pattern is known to continue, known not to continue, or not known at all."

For integers greater than 1,
2n is never congruent to 1 (mod n)
2n is congruent to 2 (mod n) whenever n is prime, and sometimes when it isn't,
is 2n ever congruent to 3 (mod n)?

No Solution Yet Submitted by Jer    
Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution 2^n mod n Comment 6 of 6 |
Here is the sequence of 2^n mod n.

0, 0, 2, 0, 2, 4, 2, 0, 8, 4, 2, 4, 2, 4, 8, 0, 2, 10, 2, 16, 8, 4, 2, 16, 7...

It might first seem like 2^n mod n is always either 0 or a power of 2. However, 2^18 mod 18=262144 mod 18=10, which is neither 0 nor a power of 2. Then, it might seem like 2^n mod n is always even. However, 2^25 mod 25=33554432 mod 25=7, which is odd. Then, it might seem like 2^n mod n is never 3. However, 2^4700063497 mod 4700063497=3.


  Posted by Math Man on 2017-10-04 14:54:22
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 (4)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2024 by Animus Pactum Consulting. All rights reserved. Privacy Information