On-line version of the NIST Digital Library of Mathematical Functions, which is an updated version of the legendary Handbook of Mathematical Functions by Milton Abramowitz and Irene Stegun.

Self-referential LZ file, by no other than Russ Cox.
See also https://research.swtch.com/nih, where Ken Thompsons code for a "trusting trust" attack is described in detail.
The unix v6 simulator at https://research.swtch.com/v6 does not work on Chrome or Brave under Android, but it does work on Firefox (Android 12).

This page contains several computer programs, written in C/C++ language (and some Matlab scripts), that implement encoding and decoding routines of popular error correcting codes (ECC), such as Reed-Solomon codes, BCH codes, the binary Golay code, a binary Goppa code, a Viterbi decoder and more. Note that no effort has been made to `optimize' most of the algorithms used in the programs below. The algorithms work well, but by no means should be used as a basis for an implementation. All these programs are free to use for academic and personal purposes only. Use them at your own discretion.

Sage is a free mathematics software system licensed under the GPL. It combines the power of many existing open-source packages into a common Python-based interface. Mission: Creating a viable free open source alternative to Magma, Maple, Mathematica and Matlab.

Discussion of methods to solve the sparse linear systems over GF(p^n) encountered in factoring and discrete logarithm problems, by B. A. LaMacchia and A. M. Odlyzko.

HTML version of the legendary Massachusetts Institute of Technology A. I. Laboratory Artificial Intelligence Memo No. 239 February 29, 1972 aka HAKMEM

A number of approximations to the Gamma function.

Interesting information about Matlab and how it manages memory (copy-on-write). From MP.

Numerical algorithm for the inverse of the normal CDF, with implementations in several programming languages.

An interesting algorithm for finding the roots of polynomials, from a tip on Matheplanet.