Function: Catalan
Section: transcendental
C-Name: mpcatalan
Prototype: p
Help: Catalan=Catalan(): Catalan's number with current precision.
Description:
 ():real:prec        mpcatalan($prec)
Doc: Catalan's constant $G = \sum_{n>=0}\dfrac{(-1)^n}{(2n+1)^2}=0.91596\cdots$.
 Note that \kbd{Catalan} is one of the few reserved names which cannot be
 used for user variables.
