18 Orthogonal PolynomialsClassical Orthogonal Polynomials

§18.13 Continued Fractions

We use the terminology of §1.12(ii). The following formulae are explicit cases of (18.2.34)–(18.2.36); this area is fully explored in §§18.30(vi) and 18.30(vii).

Chebyshev

Tn⁡(x) is the denominator of the nth approximant to:

18.13.1 −1x+−12⁢x+−12⁢x+⁢⋯,

and Un⁡(x) is the denominator of the nth approximant to:

18.13.2 −12⁢x+−12⁢x+−12⁢x+⁢⋯.

Legendre

Pn⁡(x) is the denominator of the nth approximant to:

18.13.3 a1x+−1232⁢x+−2353⁢x+−3474⁢x+⁢⋯,

where a1 is an arbitrary nonzero constant.

Laguerre

Ln⁡(x) is the denominator of the nth approximant to:

18.13.4 a11−x+−1212⁢(3−x)+−2313⁢(5−x)+−3414⁢(7−x)+⁢⋯,

where a1 is again an arbitrary nonzero constant.

Hermite

Hn⁡(x) is the denominator of the nth approximant to:

18.13.5 12⁢x+−22⁢x+−42⁢x+−62⁢x+⁢⋯.

See also Cuyt et al. (2008, pp. 91–99).