Function: besselj
Section: transcendental
C-Name: jbessel
Prototype: GGp
Help: besselj(nu,x): J-bessel function of index nu and argument x.
Doc: $J$-Bessel function of index \var{nu} and
 argument $x$. If $x$ converts to a power series, the initial factor
 $(x/2)^\nu/\Gamma(\nu+1)$ is omitted (since it cannot be represented in PARI
 when $\nu$ is not integral).
