# Links

**LMFDB**

The L-functions and Modular Forms Database is an extensive online database of mathematical objects arising in number theory, including number fields, elliptic curves, modular forms, L-functions and more.

**SageMathCloud**

Sage is an open-source computer algebra system that includes extensive support for number theory.
SageMathCloud provides a notebook interface to sage that runs in any browser and is hosted on an external computing cluster; no software installation is required and there is no cost to register for an account.
You can also **download** a copy of Sage to run on your own machine if you wish.

**PARI/GP**

PARI/GP is an open-source computer algebra system designed for fast computations in number theory. PARI is a fast C-library and GP is a script language interface to PARI that runs in an interactive shell (command-line only, no browser interface). Many Sage functions are implemented using PARI (you can directly call PARI and GP functions from within sage).

**Magma**

Magma is a closed-source computer algebra system focused on number theory, group theory, and algebraic geometry.
There is a handy **online calculator** for quick calculations, and a command line interface that you can run from many of the math department servers (type **magma** at the command line).