Rafael S. González D'león

Links to databases of Mathematical objects

The On-Line Encyclopedia of Integer Sequences

Gabriele Nebe and Neil Sloane's Catalogue of Lattices

ATLAS of Finite Group Representations

NIST Digital Library of Mathematical Functions

A Database of Graphs in Combinatorica Format

A Database of Matroids

Catalog of Oriented Matroids

The Modular Forms Database

Links to repositories with mathematical knowledge

Tricki-Problem solving

Wolfram MathWorld

Links to databases of open problems in Mathematics

Open problem garden