Perfect Numbers

Aliquot - Sequences with initial term up to 10,000, by Christophe Clavier.
http://christophe.clavier.free.fr/Aliquot/site/Aliquot.html

Aliquot Sequences - Juan L. Varona's work on aliquot sequences examines sequences with start values up to 10000, and traces them to large composite values.
http://www.unirioja.es/dptos/dmc/jvarona/aliquot.html

Cubes of Perfection - From Ivars Peterson's MathTrek column in MAA Online. Curious relationships satisfied by perfect numbers.
http://www.maa.org/mathland/mathtrek_5_18_98.html

On a Generalization of Perfect Numbers - J. L. Pe introduces perfect numbers relative to an arithmetical function f. Under this scheme, the usual perfect numbers are just one among many species of "f-perfect numbers". Several open problems and examples of perfect number sets are given, as well as a few f-amicable pairs.
http://www.geocities.com/windmill96/fperfect/fperfect.html

Aliquot Sequences - Statistics by Wolfgang Creyaufmueller, including many tables and links to factoring sites and software.
http://www.aliquot.de/aliquote.htm

Tables of Aliquot Cycles - Data for various kinds up to 10^12, including unitary, infinitary, exponential, augmented and reduced varieties.
http://amicable.homepage.dk/tables.htm

Multiply Perfect Numbers - Up-to-date information on multiperfect numbers and searchable database maintained by Achim Flammenkamp.
http://wwwhomes.uni-bielefeld.de/achim/mpn.html

Perfect Numbers - Harry J. Smith's pages of the mathematics behind perfect numbers, aliquot sequences and Mersenne numbers. Includes program listings and e-mail archives.
http://www.geocities.com/hjsmithh/Perfect.html

Perfect Number - from MathWorld - Definitions and references.
http://mathworld.wolfram.com/PerfectNumber.html

Perfect Numbers - A detailed history of the quest for perfect numbers, from Euclid to their present-day Mersenne discoveries.
http://www-history.mcs.st-and.ac.uk/history/HistTopics/Perfect_numbers.html

Aliquot Sequences - Aliquot sequences arise in iterating the sum-of-divisors function s. Bosma has calculated tables up to start value 50,000 and 80 digits.
http://www.math.ru.nl/~bosma/research/nuth/ali.html

Amicable Numbers - Observations on amicable pairs and their distribution, including Harshad and Happy Amicable pairs.
http://www.shyamsundergupta.com/amicable.htm

Aliquot Sequences - Results and software from Paul Zimmermann, addressing the Catalan Conjecture and working on the difficult "Lehmer Five" sequences.
http://www.loria.fr/~zimmerma/records/aliquot.html