Besselj
Besselj (n, z)
The Besselj function returns the Bessel function of the first kind, Jn (z ), of ordern and argument z. Supersedes the original bessJ function, which is supported for backwards compatibility only.
If z is real, a real value is returned, which means that if z is also negative, Besselj returns NaN unless n is an integer.
For complex z a complex value is returned, and there are no restrictions on z except for possible overflow.
Details
The calculation is performed using the SLATEC library. The function supports fractional and negative orders n, as well as real or complex arguments z.