Looking for a recursion relation

In summary, the conversation discussed an equation that the person was having trouble searching for information on. The equation is f(n + 1) = 2 - \dfrac{d(n)}{f(n)}, where d(n) is arbitrary and non-linear, making it difficult to find a closed form solution. The equation can also be viewed as a non-linear difference equation or a continued fraction. The person has not been able to find a general approach or solution and it was noted that it is impossible to make any general conclusions without knowing the specific form of d(n). Numerical solutions are possible, but a closed form solution is unlikely.
  • #1
topsquark
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I don't know how to do a search for information on a specific equation. It's \(\displaystyle f(n + 1) = 2 - \dfrac{d(n)}{f(n)}\), where d(n) is more or less arbitrary. It came up in some work I've been doing and I can't seem to get anywhere with it. Being non-linear it may not even have a closed form solution. There are two other ways to look at it. It's a non-linear difference equation: \(\displaystyle f \Delta f + f(f - 2) = d\) and it can also be considered as a continued fraction. (I'm going to be looking up that idea tonight.)

Any thoughts?

-Dan
 
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  • #2
topsquark said:
Any thoughts?
Yes, I think that it is impossible to make any general conclusions as the answer depends completey on ## d(n) ##.
 
  • #3
Yes, thank you. I have found (but not proven) that this equation cannot be solved in general. I haven't even found a general way to approach it. It is a very annoying little equation!

-Dan

Addendum: Well, I should say "does not have closed form solutions in general." We can always do it numerically.
 

FAQ: Looking for a recursion relation

What is a recursion relation?

A recursion relation is a mathematical formula that defines a sequence or set of values in terms of previous values in the sequence. It involves using the same formula repeatedly to generate new values.

Why is a recursion relation useful?

Recursion relations are useful because they allow us to define and solve problems in a concise and efficient way. They are often used in computer science and mathematics to solve complex problems that involve repeating patterns or structures.

How do you create a recursion relation?

To create a recursion relation, you need to identify the pattern or relationship between the values in the sequence. This can be done by observing the values and looking for a repeating pattern. Once the pattern is identified, it can be expressed in a mathematical formula that involves previous values in the sequence.

What are some common examples of recursion relations?

Some common examples of recursion relations include the Fibonacci sequence, the factorial function, and the Towers of Hanoi problem. These are all problems that involve repeating patterns or structures and can be solved using recursion relations.

What are the advantages and disadvantages of using recursion relations?

The advantages of using recursion relations include their ability to solve complex problems in a concise and elegant way, and their usefulness in computer science and mathematics. However, they can also be difficult to understand and implement correctly, and may not always be the most efficient solution for a problem.

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