Find the 100th term of a given sequence.

In summary: I see...For me, my interests lie in trigonometry and sequences and series, which I think is a shameful thing to just like mathematics in these two narrow fields of mathematics...(Blush)In summary, the conversation discusses the increasing sequence 1, 3, 4, 9, 10, 12, 13... consisting of all positive integers that are either powers of 3 or the sum of distinct powers of 3. The 100th term of this sequence is found to be $3^6+3^5+3^2$. The participants also share their interests in mathematics, including combinatorics, geometry, discrete math, relativity, and non-Euclidean geometry. One of them
  • #1
anemone
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The increasing sequence 1, 3, 4, 9, 10, 12, 13 ... consists of all those positive integers which are powers of 3 or sum of distinct powers of 3. Find the 100th term of this sequence.
 
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  • #2
anemone said:
The increasing sequence 1, 3, 4, 9, 10, 12, 13 ... consists of all those positive integers which are powers of 3 or sum of distinct powers of 3. Find the 100th term of this sequence.

Let $n=(a_ka_{k-1}\ldots a_1a_0)_2$. Then the $n$-th number in the sequence is $3^ka_k+3^{k-1}a_{k-1}\cdots+3^1a_1+a_0$. It hinges on the fact that $3^{r+1}>1+3+\cdots+3^r$. Therefore the 100th number is $3^6+3^5+3^2$.
 
  • #3
caffeinemachine said:
Let $n=(a_ka_{k-1}\ldots a_1a_0)_2$. Then the $n$-th number in the sequence is $3^ka_k+3^{k-1}a_{k-1}\cdots+3^1a_1+a_0$. It hinges on the fact that $3^{r+1}>1+3+\cdots+3^r$. Therefore the 100th number is $3^6+3^5+3^2$.

Hi caffeinemachine, thanks for participating in the problem and your answer is correct.:)

I want also to say that at MHB, we are never short of talented maths experts here, and I've gained some very useful insights from the site, and for this I am so thankful!;)
 
  • #4
anemone said:
Hi caffeinemachine, thanks for participating in the problem and your answer is correct.:)

I want also to say that at MHB, we are never short of talented maths experts here, and I've gained some very useful insights from the site, and for this I am so thankful!;)
Keep such problems coming anemone!
 
  • #5
caffeinemachine said:
Keep such problems coming anemone!

Hey caffeinemachine, are you one of the ardent fans of sequences and series? (Nerd)
 
  • #6
anemone said:
Hey caffeinemachine, are you one of the ardent fans of sequences and series? (Nerd)
Not really.. In the olympiad genre I am an 'ardent fan' of Combinatorics and Geometry questions. In curriculum mathematics I like Discrete math the most, esp Algebra and Combinatorics. And among the mathematical disciplines in which I am a newbie I find Relativity and Non Euclidean Geometry the most fascinating and Romantic.

- - - Updated - - -

anemone said:
Hey caffeinemachine, are you one of the ardent fans of sequences and series? (Nerd)
How about you? Your math interests?
 
  • #7
caffeinemachine said:
Not really.. In the olympiad genre I am an 'ardent fan' of Combinatorics and Geometry questions. In curriculum mathematics I like Discrete math the most, esp Algebra and Combinatorics. And among the mathematical disciplines in which I am a newbie I find Relativity and Non Euclidean Geometry the most fascinating and Romantic.

- - - Updated - - -How about you? Your math interests?

I see...

For me, my interests lie in trigonometry and sequences and series, which I think is a shameful thing to just like mathematics in these two narrow fields of mathematics...(Blush)
 

Related to Find the 100th term of a given sequence.

1. What is a sequence?

A sequence is a list of numbers that follow a specific pattern or rule. Each number in the sequence is called a term.

2. How do you find the 100th term of a given sequence?

To find the 100th term of a given sequence, you need to know the pattern or rule that the sequence follows. Then, you can either use a formula or manually calculate each term until you reach the 100th term.

3. Can there be more than one way to find the 100th term of a given sequence?

Yes, there can be multiple ways to find the 100th term of a given sequence depending on the pattern or rule that the sequence follows. Some sequences may have a simple formula, while others may require more complex calculations.

4. Is it important to know the pattern or rule of a sequence to find the 100th term?

Yes, it is crucial to know the pattern or rule of a sequence in order to find the 100th term accurately. Without understanding the pattern, you may end up with an incorrect answer.

5. Can you use a computer program to find the 100th term of a given sequence?

Yes, you can use a computer program to find the 100th term of a given sequence. There are various mathematical software and programming languages that can help with this task, making it faster and more efficient.

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