Finding general term of a sequence

In summary, the conversation discusses finding the general term of a sequence with a given starting point. The hint provided is to take differences "6 levels deep" and the resulting expression is A_n = A_(n-1) * (n+1) + 2(n+1). The next term is given as 362878 and the correct solution is determined to be (n+1)! - 2.
  • #1
Panphobia
435
13

Homework Statement



Find the general term of

0, 4, 22, 118, 718, 5038, 40318

if a1 = 0, a2 = 4 and so on.


The Attempt at a Solution



I have tried getting the differences between them, even going 4 levels deep, but that isn't working obviously, I tried seeing if the ratios are the same, but they aren't. I really don't know what to do, I just need a hint to get this problem going. Thanks for your time!
 
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  • #2
The next term is 362878. Doesn't seem very hard, I guess you just have to see the trick.
 
  • #3
There are, of course, an infinite number of such sequences. There is, for example a unique polynomial, of degree 6 or less, passing through those 7 points. To get that you would have to take differences "6 levels deep".
 
  • #4
phinds said:
The next term is 362878. Doesn't seem very hard, I guess you just have to see the trick.
I'm not the original poster but still interested in solving this problem. Following your hint, the following is the expression I ended up with.

A_n = A_(n-1) * (n+1) + 2(n+1)

How do I go about resolving A_(n-1) to a function/expression in terms of n?
 
  • #5
nmr said:
I'm not the original poster but still interested in solving this problem. Following your hint, the following is the expression I ended up with.

A_n = A_(n-1) * (n+1) + 2(n+1)

How do I go about resolving A_(n-1) to a function/expression in terms of n?

You have to take an assumed starting point, I think. I certainly did, but maybe someone with more math experience can give you an answer.

By the way, I obviously could have just posted the answer myself, but I thought I'd give the OP another shot at it, knowing that it isn't hard. I think you showed poor form in not doing the same.

The point of this forum is to help others figure things out, NOT to spoon feed them answers.
 
  • #6
Going six levels deep would only give me one number left, I am thinking you would need at least 3 to see if the differences are the same. By the way, for the last value I got 18806. I am kind of stumped again. Yes I typed the sequence into wolfram alpha and got answers with factorials everywhere, I know I wouldn't have got that on my own.
 
Last edited:
  • #7
phinds said:
You have to take an assumed starting point, I think. I certainly did, but maybe someone with more math experience can give you an answer.

By the way, I obviously could have just posted the answer myself, but I thought I'd give the OP another shot at it, knowing that it isn't hard. I think you showed poor form in not doing the same.

The point of this forum is to help others figure things out, NOT to spoon feed them answers.

It is even poorer form to post an incorrect solution, as the previous OP has done.
 
  • #8
I figured it out, (N+1)! - 2, thank you all!
 

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.

What is the general term of a sequence?

The general term of a sequence is an algebraic expression that allows you to find any term in the sequence by plugging in the term number. It is usually denoted as an, where n represents the term number.

How do you find the general term of a sequence?

To find the general term of a sequence, you need to examine the given sequence and look for a pattern. Once you have identified the pattern, you can use it to create an algebraic expression for the general term.

What are some common types of sequences?

Some common types of sequences include arithmetic sequences, geometric sequences, and recursive sequences. In arithmetic sequences, each term is found by adding a constant value to the previous term. In geometric sequences, each term is found by multiplying the previous term by a constant value. In recursive sequences, each term is found by using the previous term in the sequence.

Why is finding the general term of a sequence important?

Finding the general term of a sequence allows us to predict and calculate any term in the sequence without needing to list out every term. It also helps us understand the pattern and behavior of the sequence, which can be useful in various applications, such as predicting future values or solving mathematical problems.

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