PARI/GP

URL: http://pari.math.u-bordeaux.fr
Contact: pari@math.u-bordeaux.fr

PARI/GP is a widely used Computer Algebra System designed for fast computations in number theory, but also contains a large number of other useful functions to compute with mathematical entities such as matrices, power series, algebraic or p-adic numbers, etc., and a lot of transcendental functions. PARI is also available as a C library to allow for faster computations.

Citation:

@preamble{"\usepackage{url}"}
@manual{PARI,
  title = "{PARI/GP, version {\tt 2.1.5}}",
  note = "\url{http://pari.math.u-bordeaux.fr/}",
  address = {Bordeaux},
  year = 2003
}
% no author mentioned: using "The PARI group" was not too informative ]