There are several high-level computer languages with huge libraries of mathematical features built into them. The three most popular are probably the Computational Algebra Group’s Magma, Waterloo’s Maple, Wolfram’s Mathematica and William Stein’s Sage, which is free. It is likely that Mathworks’ Matlab has more users than the other four put together, but it is aimed at a broader market.
Popular mathematical sites include:
- Neil Sloane’s On-line Encyclopedia of Integer Sequences.