Three-term recurrence relation

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In mathematics, and especially in numerical analysis, a homogeneous linear three-term recurrence relation (TTRR, the qualifiers "homogeneous linear" are usually taken for granted) [1] is a recurrence relation of the form

Contents

for

where the sequences and , together with the initial values govern the evolution of the sequence .

Applications

If the and are constant and independent of the step index n, then the TTRR is a Linear recurrence with constant coefficients of order 2. Arguably the simplest, and most prominent, example for this case is the Fibonacci sequence, which has constant coefficients .

Orthogonal polynomials Pn all have a TTRR with respect to degree n,

where An is not 0. Conversely, Favard's theorem states that a sequence of polynomials satisfying a TTRR is a sequence of orthogonal polynomials.

Also many other special functions have TTRRs. For example, the solution to

is given by the Bessel function . TTRRs are an important tool for the numeric computation of special functions.

TTRRs are closely related to continuous fractions.

Solution

Solutions of a TTRR, like those of a linear ordinary differential equation, form a two-dimensional vector space: any solution can be written as the linear combination of any two linear independent solutions. A unique solution is specified through the initial values . [2]

See also

Literature

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References

  1. Gi, Segura, Temme (2007), Chapter 4.1
  2. Gi, Segura, Temme (2007), Chapter 4.1