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

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

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

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

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

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

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

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

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

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

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