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13 Confluent Hypergeometric FunctionsKummer Functions

§13.11 Series

For z,

13.11.1 M(a,b,z)=Γ(a12)e12z(14z)12as=0(2a1)s(2ab)s(b)ss!(a12+s)Ia12+s(12z),
a+12,b0,1,2,,
13.11.2 M(a,b,z)=Γ(ba12)e12z(14z)ab+12×s=0(1)s(2b2a1)s(b2a)s(ba12+s)(b)ss!Iba12+s(12z),
ba+12,b0,1,2,.

(13.6.9), (13.6.11_1) and (13.6.11_2) are special cases.

13.11.3 𝐌(a,b,z)=e12zs=0As(b2a)12(1bs)(12z)12(1b+s)Jb1+s(2z(b2a)),

where

13.11.4 A0 =1,
A1 =0,
A2 =12b,
(n+1)An+1 =(n+b1)An1+(2ab)An2,
n=2,3,4,.

For additional expansions combine (13.14.4), (13.14.5), and §13.24. For other series expansions see Tricomi (1954, §1.8), Hansen (1975, §§66 and 87), Prudnikov et al. (1990, §6.6), López and Temme (2010a) and López and Pérez Sinusía (2014). See also §13.13.