Algorithmic Number Theory: Tables and Links: Compiled by Noam Elkies.
Algorithms for Solving Index Form Equations and Computing Power Integral Bases: Lists of results, description of algorithms and tables of numerical data, by István Gaál.
Carmichael and Perrin: The 150 Carmichael numbers out of 246683 up to 10^16 that are Perrin pseudoprimes.
Carmichael Numbers and Lehmer's Problem: Carmichael numbers n up to 10^9 together with phi(n), (n-1)/phi(n) and the factorization of n. Compiled by Jan Kristian Haugland.
Cubic Field Extensions: Tables and results on cubic number fields by Daniel A. Mayer.
Curves of Genus 2: FTP site maintained by Victor Flynn. Formulae for Jacobian arithmetic and Maple algorithms.
Database for Polynomials over the Rationals: By Jürgen Klüners and Gunter Malle. Polynomials for all transitive groups up to degree 15, for most of the possible combinations of signature and Galois group. Up to degree 7 the fields with minimal (absolute) discriminant with given Galois group and signature are included.
Database of Local Fields: By John W. Jones and David P. Roberts. Tables of low degree extensions of Qp, for small p.
Dedekind Zeta Functions: Tabulated by Eyal Goren using Pari.
Enumeration of Twin Primes and Brun's Constant: Enumeration of the twin primes, and the sum of their reciprocals, to 1.6 × 10^15. An improved estimate is obtained for Brun's constant, B2 = 1.90216 05824 ± 0.00000 00030. Error analysis is presented to support the opinion that the stated error bound represents a 99 % confidence level.
Extended Counts of Twin Primes: By Thomas Nicely. Counts in decades up to 10^12 then in steps of 10^12 up to 3.10^15, giving 3,310,517,800,844 pairs.
Factorization Tables: Tables of the factorization of sigma(n).
Fermat Near-misses: Noam Elkies. Approximate solutions of x^n + y^n = z^n in integers with 0 < x <= y < z < 2^23 and n in [4,20].
Imaginary Quadratic Fields: Tables of the fields with class number at most 23.
Multiply Perfect Numbers: Over 2000 multiperfect numbers sorted by numerical value and by factorisation.
Number Field Tables: FTP site at the University of Bordeaux. Fields of degree up to 7.
Number Fields with Prescribed Ramification: Number fields of degree up to seven ramified at only a few small primes.
Practical Numbers: A number is practical if all smaller numbers are sums of distinct divisors. Tables compiled by Guiseppe Melfi.
Pseudoprimes and Carmichael Numbers: Tables of the Fermat pseudoprimes base 2 up to 10^13 and Carmichael numbers up to 10^17 compiled by Richard Pinch.
Table of Masses of 32-dimensional Even Unimodular Lattices: With any given root system. Oliver King.
Tables and Computations: Browsable interfaces to tables and computations on elliptic curves, quadratic forms, and modular forms.
Tables of Number Fields: Hilbert class field of totally real fields of degree 2, 3 and 4; Totally real fields with small root discriminant; Totally real quintic dihedral fields. By Xavier-François Roblot.
Tables of Primes: Various tables available on DVD or CD. Free copies available for donation to some institutions.
The First 100,000 Prime Numbers: A Project Gutenberg etext.
The First 28,915 Odd Primes: Tabulated using a simple C program.
The First 498 Bernoulli Numbers: A Project Gutenberg etext.
The Positive Integers: Information about the positive integers, with counts of some number-theoretic functions, maintained by Saqib Kadri.
The Value of Zeta(3) to 1,000,000 Decimal Digits: A Project Gutenberg etext.
Vanishing Fermat Quotients: R. Ernvall and T. Metsänkylä. Tables of the pairs (p,k) such that the Fermat quotient q(k) = (k^{p-1}-1)/p vanishes mod p. The tables cover the primes p up to one million and, for each prime, the range 1 < k < p.
Zeroes of the Riemann Zeta Function: By Andrew Odlyzko. The first 100,000 to 8 places, the first 1000 to 1000 places.