13 Confluent Hypergeometric Functions Whittaker Functions 13.16 Integral Representations 13.18 Relations to Other Functions

§13.17 Continued Fractions

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Keywords:: Whittaker functions, continued fractions
Notes:: See Jones and Thron (1980, Theorems 6.3 and 6.5).
Permalink:: http://dlmf.nist.gov/13.17
See also:: Annotations for Ch.13

If $\kappa,\mu\in\mathbb{C}$ such that $\mu\pm(\kappa-\tfrac{1}{2})\neq-1,-2,-3,\dots$ , then

13.17.1 $\frac{\sqrt{z}M_{\kappa,\mu}\left(z\right)}{M_{\kappa-\frac{1}{2},\mu+\frac{1}% {2}}\left(z\right)}=1+\cfrac{u_{1}z}{1+\cfrac{u_{2}z}{1+\cdots}},$

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Symbols:: $M_{\NVar{\kappa},\NVar{\mu}}\left(\NVar{z}\right)$ : Whittaker confluent hypergeometric function, : complex variable and $u_{n}$ : continued fraction coefficients
Permalink:: http://dlmf.nist.gov/13.17.E1
Encodings:: TeX, pMML, png
See also:: Annotations for §13.17 and Ch.13

where

13.17.2

$u_{2n+1}=-\frac{\frac{1}{2}+\mu+\kappa+n}{(2\mu+2n+1)(2\mu+2n+2)},$

$u_{2n}=\frac{\frac{1}{2}+\mu-\kappa+n}{(2\mu+2n)(2\mu+2n+1)}.$

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Defines:: $u_{n}$ : continued fraction coefficients (locally)
Symbols:: : nonnegative integer
Permalink:: http://dlmf.nist.gov/13.17.E2
Encodings:: TeX, TeX, pMML, pMML, png, png
See also:: Annotations for §13.17 and Ch.13

This continued fraction converges to the meromorphic function of on the left-hand side for all $z\in\mathbb{C}$ . For more details on how a continued fraction converges to a meromorphic function see Jones and Thron (1980).

If $\kappa,\mu\in\mathbb{C}$ such that $\mu+\tfrac{1}{2}\pm(\kappa+1)\neq-1,-2,-3,\dots$ , then

13.17.3 $\frac{W_{\kappa,\mu}\left(z\right)}{\sqrt{z}W_{\kappa-\frac{1}{2},\mu-\frac{1}% {2}}\left(z\right)}=1+\cfrac{v_{1}/z}{1+\cfrac{v_{2}/z}{1+\cdots}},$

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