Properties based on the sum-of-divisors function s(n), including perfect and multiperfect numbers, aliquot sequences, amicable pairs and sociable chains.
Sequences with initial term up to 10,000, by Christophe Clavier.
Juan L. Varona's work on aliquot sequences examines sequences with start values up to 10000, and traces them to large composite values.
Results and software from Paul Zimmermann, addressing the Catalan Conjecture and working on the difficult "Lehmer Five" 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.
Statistics by Wolfgang Creyaufmueller, including many tables and links to factoring sites and software.
Observations on amicable pairs and their distribution, including Harshad and Happy Amicable pairs.
Multiply Perfect Numbers
Up-to-date information on multiperfect numbers and searchable database maintained by Achim Flammenkamp.
Perfect Number - from MathWorld
Definitions and references.
A detailed history of the quest for perfect numbers, from Euclid to their present-day Mersenne discoveries.
Last update:February 13, 2015 at 7:15:05 UTC