Tables

Algorithmic Number Theory: Tables and Links - Compiled by Noam Elkies.
http://www.math.harvard.edu/~elkies/compnt.html

A Database for Number Fields - 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.
http://www.math.uni-duesseldorf.de/~klueners/minimum/

The First 28,915 Odd Primes - Tabulated using a simple C program.
http://www.newdream.net/~sage/old/numbers/primeodd.htm

Fermat Near-misses - Noam Elkies. Approximate solutions in integers.
http://www.math.harvard.edu/~elkies/ferm.html

The Positive Integers - Information about the positive integers, with counts of some number-theoretic functions, maintained by Saqib Kadri.
http://www.positiveintegers.org/

Cubic Field Extensions - Tables and results on cubic number fields by Daniel A. Mayer.
http://www.algebra.at/CubicNumberFields.htm

Dedekind Zeta Functions - Tabulated by Eyal Goren using Pari.
http://www.math.mcgill.ca/goren/ZetaValues/zeta.html

Zeroes of the Riemann Zeta Function - By Andrew Odlyzko. The first 100,000 to 8 places, the first 1000 to 1000 places.
http://www.dtc.umn.edu/~odlyzko/zeta_tables/

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.
http://www.chalcedon.demon.co.uk/rgep/carpsp.html

Tables and Computations - Browsable interfaces to tables and computations on elliptic curves, quadratic forms, and modular forms.
http://www.math.utexas.edu/users/tornaria/cnt/

Table of Masses of 32-dimensional Even Unimodular Lattices - With any given root system. Oliver King.
http://www.csua.berkeley.edu/~ok/rootmass.txt.gz

Factorization Tables - Tables of the factorization of sigma(n).
http://www-staff.maths.uts.edu.au/~rons/fact/fact.htm

The First 498 Bernoulli Numbers - A Project Gutenberg etext.
http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2586

Database of Local Fields - By John W. Jones and David P. Roberts. Tables of low degree extensions of Qp, for small p.
http://math.asu.edu/~jj/localfields/

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.
http://www.math.klte.hu/~igaal/algorithm.htm

Multiply Perfect Numbers - Over 2000 multiperfect numbers sorted by numerical value and by factorisation.
ftp://ftp.cs.arizona.edu/xkernel/rcs/mpfn.html

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.
http://igd.univ-lyon1.fr/~roblot/tables.html

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.
http://www.trnicely.net/twins/tabpi2.html

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.
http://home.no.net/zamunda/carmichael.txt

The Value of Zeta(3) to 1,000,000 Decimal Digits - A Project Gutenberg etext.
http://digital.library.upenn.edu/webbin/gutbook/lookup?num=2583

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.
http://users.utu.fi/taumets/fermat/fermat.htm

Practical Numbers - A number is practical if all smaller numbers are sums of distinct divisors. Tables compiled by Giuseppe Melfi.
http://www.dm.unipi.it/gauss-pages/melfi/public_html/pratica.html

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.
http://www.trnicely.net/twins/twins2.html

Number Fields with Prescribed Ramification - Number fields of degree up to seven ramified at only a few small primes.
http://math.la.asu.edu/~jj/numberfields/

Number Field Tables - FTP site at the University of Bordeaux. Fields of degree up to 7.
ftp://megrez.math.u-bordeaux.fr/pub/numberfields

Imaginary Quadratic Fields - Tables of the fields with class number at most 23.
http://www.numbertheory.org/classnos/

The First 100,000 Prime Numbers - A Project Gutenberg etext.
http://digital.library.upenn.edu/webbin/gutbook/lookup?num=65