Digital Library of Mathematical Functions
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18 Orthogonal PolynomialsClassical Orthogonal Polynomials

§18.13 Continued Fractions

We use the terminology of §1.12(ii).

Chebyshev

\mathop{T_{{n}}\/}\nolimits\!\left(x\right) is the denominator of the nth approximant to:

18.13.1\cfrac{-1}{x+\cfrac{-1}{2x+\cfrac{-1}{2x+}}}\cdots,

and \mathop{U_{{n}}\/}\nolimits\!\left(x\right) is the denominator of the nth approximant to:

18.13.2\cfrac{-1}{2x+\cfrac{-1}{2x+\cfrac{-1}{2x+}}}\cdots.

Legendre

\mathop{P_{{n}}\/}\nolimits\!\left(x\right) is the denominator of the nth approximant to:

18.13.3\cfrac{a_{1}}{x+\cfrac{-\frac{1}{2}}{\frac{3}{2}x+\cfrac{-\frac{2}{3}}{\frac{5%
}{3}x+\cfrac{-\frac{3}{4}}{\frac{7}{4}x+}}}}\cdots,

where a_{1} is an arbitrary nonzero constant.

Laguerre

\mathop{L_{{n}}\/}\nolimits\!\left(x\right) is the denominator of the nth approximant to:

18.13.4\cfrac{a_{1}}{1-x+\cfrac{-\frac{1}{2}}{\frac{1}{2}(3-x)+\cfrac{-\frac{2}{3}}{%
\frac{1}{3}(5-x)+\cfrac{-\frac{3}{4}}{\frac{1}{4}(7-x)+}}}}\cdots,

where a_{1} is again an arbitrary nonzero constant.

Hermite

\mathop{H_{{n}}\/}\nolimits\!\left(x\right) is the denominator of the nth approximant to:

18.13.5\cfrac{1}{2x+\cfrac{-2}{2x+\cfrac{-4}{2x+\cfrac{-6}{2x+}}}}\cdots.

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