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

Home > Numbers
38s and Bunches of 1s (Posted on 2017-06-30) Difficulty: 3 of 5
Prove every number in the sequence 38, 381, 3811, 38111, 381111, ... is composite.

See The Solution Submitted by Brian Smith    
Rating: 4.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Another way of seeing part of it | Comment 5 of 7 |
for any term x, the next term is 10x+1, 
the term after that is 10(10x+1)+1 = 100x+11,
the term after that is 10(10(10x+1)+1)+1 = 1000x+111

111 = 3*37 so if any term is divisible by 3, the third term after that is too.  Same goes for 37.

I'm not sure how this explains the 2333333 

  Posted by Jer on 2017-06-30 14:03:47
Please log in:
Remember me:
Sign up! | Forgot password

Search body:
Forums (3)
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

Copyright © 2002 - 2020 by Animus Pactum Consulting. All rights reserved. Privacy Information