## Welcome to BrainDen.com - Brain Teasers Forum

 Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account. As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends. Of course, you can also enjoy our collection of amazing optical illusions and cool math games. If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top. If you have a website, we would appreciate a little link to BrainDen. Thanks and enjoy the Den :-)
Guest Message by DevFuse

# No First-Hand-Neighbors!!

10 replies to this topic

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 06 July 2013 - 09:20 PM

Create the shortest possible sequence (using numbers from 1,2,...n) such that no number is next to its first-hand neighbors (e.g. the number 2 cannot be next to numbers 1 and 3, which are its first-hand neighbors).

e.g.

1,6,3,5,2,4,7  Here is a sequence using 7 numbers that meets the requirement.

• 0

### #2 Nins_Leprechaun

Nins_Leprechaun

Junior Member

• Members
• 37 posts

Posted 06 July 2013 - 10:41 PM   Best Answer

Spoiler for

• 0

### #3 bonanova

bonanova

bonanova

• Moderator
• 6148 posts
• Gender:Male
• Location:New York

Posted 07 July 2013 - 06:29 AM

• 0

Vidi vici veni.

### #4 witzar

witzar

• Members
• 233 posts

Posted 07 July 2013 - 03:37 PM

Clearly empty sequence (length 0) wins the contest..
• 0

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 07 July 2013 - 04:52 PM

the sequence must start at 1 and go to some n (consecutively) where n does not equal 1.

Edited by BMAD, 07 July 2013 - 04:53 PM.

• 0

### #6 witzar

witzar

• Members
• 233 posts

Posted 07 July 2013 - 05:00 PM

the sequence must start at 1 and go to some n (consecutively) where n does not equal 1.

Now it's a different story. BTW "best answer" sequence starts with 3 not with 1.

• 0

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 07 July 2013 - 05:40 PM

I am sorry, I am working on translating to English better. I mean to say that the numbers you use must contain the sequence from 1 to some N but don't have to start that way. So 1, 3, 5, 2, and 4 are fine since it contains numbers 1-5 and no first hand neighbors.
• 0

### #8 bonanova

bonanova

bonanova

• Moderator
• 6148 posts
• Gender:Male
• Location:New York

Posted 08 July 2013 - 01:59 AM

It was clear to me what you were asking.
I just included, for fun, something outside the "box".

Your English is fantastically good, even for a first-language writer,
No need to apologize.

Did I hear somewhere that Russian is your first language?
• 0

Vidi vici veni.

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 08 July 2013 - 03:29 AM

My first language is Ukrainian but I do speak Russian sufficiently.

• 0

### #10 bonanova

bonanova

bonanova

• Moderator
• 6148 posts
• Gender:Male
• Location:New York

Posted 10 July 2013 - 10:55 AM

My first language is English and I'm still learning it. My writing is OK but my speech needs work.

• 0

Vidi vici veni.

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users