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§10.51 Recurrence Relations and Derivatives

Contents
  1. §10.51(i) Unmodified Functions
  2. §10.51(ii) Modified Functions

§10.51(i) Unmodified Functions

Let f_{n}(z) denote any of \mathsf{j}_{n}\left(z\right), \mathsf{y}_{n}\left(z\right), {\mathsf{h}^{(1)}_{n}}\left(z\right), or {\mathsf{h}^{(2)}_{n}}\left(z\right). Then

10.51.1
f_{n-1}(z)+f_{n+1}(z)=((2n+1)/z)f_{n}(z),
nf_{n-1}(z)-(n+1)f_{n+1}(z)=(2n+1)f_{n}^{\prime}(z),n=1,2,\dots,
10.51.2
f_{n}^{\prime}(z)=f_{n-1}(z)-((n+1)/z)f_{n}(z),n=1,2,\dots,
f_{n}^{\prime}(z)=-f_{n+1}(z)+(n/z)f_{n}(z),n=0,1,\dots.
10.51.3
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{m}(z^{n+1}f_{n}(z))=z^%
{n-m+1}f_{n-m}(z),m=0,1,\dots,n,
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{m}(z^{-n}f_{n}(z))=(-1%
)^{m}z^{-n-m}f_{n+m}(z),m=0,1,\dots.

§10.51(ii) Modified Functions

Let g_{n}(z) denote {\mathsf{i}^{(1)}_{n}}\left(z\right), {\mathsf{i}^{(2)}_{n}}\left(z\right), or (-1)^{n}\mathsf{k}_{n}\left(z\right). Then

10.51.4
g_{n-1}(z)-g_{n+1}(z)=((2n+1)/z)g_{n}(z)
ng_{n-1}(z)+(n+1)g_{n+1}(z)=(2n+1)g_{n}^{\prime}(z),n=1,2,\dotsc,
10.51.5
g_{n}^{\prime}(z)=g_{n-1}(z)-((n+1)/z)g_{n}(z),n=1,2,\dotsc,
g_{n}^{\prime}(z)=g_{n+1}(z)+(n/z)g_{n}(z),n=0,1,\dotsc.
10.51.6
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{m}(z^{n+1}g_{n}(z))=z^%
{n-m+1}g_{n-m}(z),m=0,1,\dotsc,n,
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{m}(z^{-n}g_{n}(z))=z^{%
-n-m}g_{n+m}(z),m=0,1,\dotsc.