This contains some Sage/Cython code for working with Dirichlet characters
using a numbering scheme described by Brian Conrey. I intend to eventually
get this included in Sage, but for now I am developing it separately.

Right now, to use this code, you can just use "load('dirichlet_conrey.pyx')"
from a running Sage session:

    ~$ git clone https://github.com/jwbober/conrey-dirichlet-characters
    ...
    ~$ cd conrey-dirichlet-characters/
    ~/conrey-dirichlet-characters$ sage
    ...
    sage: load('dirichlet_conrey.pyx')
    Compiling ./dirichlet_conrey.pyx...
    warning: _home_user_conrey_dirichlet_characters_dirichlet_conrey_pyx_0.pyx:938:12: Unreachable code
    sage: G = DirichletGroup_conrey(21)
    sage: G[4]*G[5]
    Dirichlet character with index 20 modulo 21


You can run "sage setup.py install" to build
it as a module and put it in your Sage python modules directory, so that you
can use it as "import dirichlet_conrey.pyx". To run the doctests, you need
to actually run setup.py to install the module.