Almost Perfect Number

A number for which the Divisor Function satisfies is called almost perfect. The only known almostperfect numbers are the A000079). Singh (1997) callsalmost perfect numbers Slightly Defective.

References

Guy, R. K. ``Almost Perfect, Quasi-Perfect, Pseudoperfect, Harmonic, Weird, Multiperfect and Hyperperfect Numbers.'' §B2 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 16 and 45-53, 1994.

Singh, S. Fermat's Enigma: The Epic Quest to Solve the World's Greatest Mathematical Problem. New York: Walker, p. 13, 1997.

Sloane, N. J. A. SequenceA000079/M1129in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.

• Entscheidungsproblem
• Enumerative Geometry
• Envelope
• Envelope Theorem
• Envyfree
• e-Perfect Number
• Epicycloid
• Epicycloid--1-Cusped
• Epicycloid--2-Cusped
• Epicycloid Evolute
• Epicycloid Involute
• Epicycloid Pedal Curve
• Epicycloid Radial Curve
• Epimenides Paradox
• Epimorphism
• Epispiral
• Epispiral Inverse Curve
• Epitrochoid
• Epitrochoid Evolute
• Epsilon
• Epsilon-Neighborhood
• Epstein Zeta Function
• Equal
• Equal by Definition
• Equal Detour Point