How to solve this functional (recurrence) equation ?

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    Functional Recurrence
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Discussion Overview

The discussion revolves around solving the functional equation F(n)^2 = n + F(n+1). Participants explore methods for addressing this type of recurrence relation, with a specific focus on finding the function F(n) and its values at specific points.

Discussion Character

  • Exploratory, Homework-related, Mathematical reasoning

Main Points Raised

  • One participant presents the functional equation and seeks methods for solving it.
  • Another participant notes that the problem is incomplete without an initial condition, suggesting that F(0) is needed.
  • A third participant states that the goal is to find F(1), providing a specific expression for it: F(1) = √(1 + √(2 + √(3 + ...))).
  • A later reply reiterates the goal of finding F(1) and questions whether the task is to find F(n) given this expression for F(1), suggesting that finding F(2) may reveal a pattern.

Areas of Agreement / Disagreement

Participants express differing views on the completeness of the problem, with some emphasizing the need for an initial condition while others focus on deriving values from the given expression for F(1). The discussion remains unresolved regarding the methods for solving the functional equation.

Contextual Notes

The discussion highlights the dependence on initial conditions and the potential for multiple interpretations of the problem statement. There are unresolved aspects regarding the derivation of F(n) from the provided expression.

jk22
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I'm in a problem where I have to solve the following functional equation :

[tex]F(n)^2=n+F(n+1)[/tex]

Does anyone know some methods to solve this kind of problems ?

A similar equation happens in Ramanujan example of root denesting : http://en.wikipedia.org/wiki/Nested_radical#Square_roots
 
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Don't know of a method. As stated the problem is incomplete - you need an initial condition (F(0) = ?).
 
The problem is to find F(1), knowing that [tex]F(1)=\sqrt{1+\sqrt{2+\sqrt{3+\ldots}}}[/tex].
 
jk22 said:
The problem is to find F(1), knowing that [tex]F(1)=\sqrt{1+\sqrt{2+\sqrt{3+\ldots}}}[/tex].

Should that be to find F(n) given that [itex]F(1)=\sqrt{1+\sqrt{2+\sqrt{3+\ldots}}}[/itex] ?

Find F(2) and the pattern becomes clear.
 

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