All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > Homework Help

Notices

Homework Help Stuck on a textbook question or coursework? Cramming for a test and need help understanding something? Post your questions and attempts here and let others help.

Reply   Post New Thread
 
Thread Tools Display Modes
  #1  
Old 03-08-2010, 11:30 PM
s3b4k s3b4k is offline
Junior Member
 
Join Date: Feb 2010
Posts: 38
Default discrete math- sequence question

I need to come up with a rule or a formula for the following:

1,2,2,2,3,3,3,3,3,5,5,5,5,5,5,5.....
Reply With Quote
  #2  
Old 03-09-2010, 12:10 AM
someonesdad someonesdad is offline
Senior Member
 
Join Date: Jul 2009
Location: Northwest USA
Posts: 1,584
Default

Hint: 2*n + 1 and primes
Reply With Quote
  #3  
Old 03-09-2010, 12:22 AM
jpanhalt jpanhalt is offline
E-book Developer
 
Join Date: Jan 2008
Location: Ohio, USA(GMT-5)
Posts: 3,619
Default

There may be more than one pattern that gives that initial sequence. One solution is: the digits 1,2,3,and 5 are primes (positive). The repeat frequencies seem to follow just the odd numbers. The next three repeat frequencies would be 9, 11 and 13. That is, the next two sequences would be nine 7's, then eleven 11's.

John
Reply With Quote
The Following User Says Thank You to jpanhalt For This Useful Post:
s3b4k (03-11-2010)
  #4  
Old 03-09-2010, 12:45 AM
s3b4k s3b4k is offline
Junior Member
 
Join Date: Feb 2010
Posts: 38
Default

ok thanks a lot for the help, but is there an exact formula i can use, or is it only solvable by explaining it?
Reply With Quote
  #5  
Old 03-11-2010, 12:34 PM
Markd77's Avatar
Markd77 Markd77 is online now
Senior Member
 
Join Date: Sep 2009
Location: Birmingham
Posts: 2,750
Blog Entries: 1
Default

1 isn't normally considered a prime if that makes any difference.
Reply With Quote
  #6  
Old 03-11-2010, 12:48 PM
jpanhalt jpanhalt is offline
E-book Developer
 
Join Date: Jan 2008
Location: Ohio, USA(GMT-5)
Posts: 3,619
Default

Sorry. Problem easily solved in the description.

http://mathworld.wolfram.com/PrimeNumber.html

John
Reply With Quote
  #7  
Old 03-11-2010, 03:09 PM
Markd77's Avatar
Markd77 Markd77 is online now
Senior Member
 
Join Date: Sep 2009
Location: Birmingham
Posts: 2,750
Blog Entries: 1
Default

I searched for the sequence on google and found this. Still no idea what it is.
Quote:
For each of these lists of integers, provide a simple formula or rule that generates the terms of an integer sequence that begins with the given list.
(a) 3, 6, 11, 18, 27, 38, 51, 66, 83,
(b) 1, 2, 2, 2, 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8,
Reply With Quote
  #8  
Old 03-11-2010, 03:59 PM
jpanhalt jpanhalt is offline
E-book Developer
 
Join Date: Jan 2008
Location: Ohio, USA(GMT-5)
Posts: 3,619
Default

For (b) the sequence starts with 1, and if there are at least 2 previous term, then the subsequent term is the sum of the previous two terms, otherwise it is 2 (or alternatively, the previous term is doubled). The replicates of each term is as in the first problem.

I am too tired to look at (a) now. Perhaps this question should have its own thread.

John

Edit: For (a) here's a reference: http://mathworld.wolfram.com/Near-SquarePrime.html

Last edited by jpanhalt; 03-11-2010 at 05:24 PM. Reason: added reference
Reply With Quote
  #9  
Old 03-11-2010, 11:19 PM
s3b4k s3b4k is offline
Junior Member
 
Join Date: Feb 2010
Posts: 38
Default

this question is driving me nuts, are the next three terms going to be 8,8,8 or 7,7,7. because it good either be prime numbers or just the sum of the previous numbers, but if its the sum of the previous numbers how do you get the two there
Reply With Quote
  #10  
Old 03-11-2010, 11:32 PM
jpanhalt jpanhalt is offline
E-book Developer
 
Join Date: Jan 2008
Location: Ohio, USA(GMT-5)
Posts: 3,619
Default

Quote:
Originally Posted by s3b4k View Post
this question is driving me nuts, are the next three terms going to be 8,8,8 or 7,7,7. because it good either be prime numbers or just the sum of the previous numbers, but if its the sum of the previous numbers how do you get the two there
There is not enough information to know for sure. The sum of the previous numbers (Fibonacci, 8) may be what your teacher wants. In either case, you have to make an explanation for the first number (or absence thereof).

John

PS, when I went to school 1 was still prime. But then, it was a public school.
Reply With Quote
The Following User Says Thank You to jpanhalt For This Useful Post:
s3b4k (03-11-2010)
Reply   Post New Thread

Tags
, , ,


Related Site Pages
Section Title
Video Lecture Troubleshooting Transistor Circuits - Transistors and Transistor Circuits
Textbook Sequences : Algebra Reference
Textbook Minterm vs maxterm solution : Karnaugh Mapping
Textbook Logic simplification with Karnaugh maps : Karnaugh Mapping
Textbook Larger 5 & 6-variable Karnaugh maps : Karnaugh Mapping
Textbook Boolean arithmetic : Boolean Algebra
Textbook Quantum physics : Solid-state Device Theory


Similar Threads
Thread Thread Starter Forum Replies Last Post
I am a math rock. Simple transposition question SgtWookie Math 10 03-03-2010 06:30 PM
infrared Liquid level detector fantabulous68 Embedded Systems and Microcontrollers 49 09-27-2009 09:18 PM
Math Question! Nishki Homework Help 7 04-27-2009 03:54 PM
convergence - math question silvrstring Homework Help 3 05-28-2008 05:34 AM
discrete math and proof braddy Math 2 09-09-2006 03:56 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 09:38 PM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.