Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

n-digit numbers created using digits 5 and 9, where no four identical digits stand side by side.

Posted on 2015-02-12
2
Medium Priority
?
151 Views
Last Modified: 2015-02-12
How many n-digit numbers can be created using only digits 5 and 9, where no four identical digits stand side by side?
0
Comment
Question by:Nusrat Nuriyev
2 Comments
 
LVL 85

Accepted Solution

by:
ozo earned 2000 total points
ID: 40606194
a[1] = 2
a[2] = 4
a[3] = 8
a[n] = a[n - 1] + a[n - 2] + a[n - 3]
https://oeis.org/A135491
0
 

Author Comment

by:Nusrat Nuriyev
ID: 40606261
ozo, also, this a[n]=a[n-1]+a[n-2]+a[n-3] gives us the n-digit numbers which can be created using only digits 5 and 9, where no three ones stand side by side. (but this does not mentioned in OEIS)

Could you explain why this sequence solves my original question? For better understanding.
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: Nadia
Linear search (searching each index in an array one by one) works almost everywhere but it is not optimal in many cases. Let's assume, we have a book which has 42949672960 pages. We also have a table of contents. Now we want to read the content on p…
Iteration: Iteration is repetition of a process. A student who goes to school repeats the process of going to school everyday until graduation. We go to grocery store at least once or twice a month to buy products. We repeat this process every mont…
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below. https://filedb.experts-exchange.com/incoming/2017/03_w12/1151775/Permutations.txt https://filedb.experts-exchange.com/incoming/201…
When cloud platforms entered the scene, users and companies jumped on board to take advantage of the many benefits, like the ability to work and connect with company information from various locations. What many didn't foresee was the increased risk…
Suggested Courses

577 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question