Unitary Perfect Number
A number 
which is the sum of its Unitary Divisors with the exception of itself.There are no Odd unitary perfect numbers, and it has been conjectured that there are only a Finite number ofA002827).
References
Guy, R. K. ``Unitary Perfect Numbers.'' §B3 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 53-59, 1994. Sloane, N. J. A. SequenceA002827/M4268in ``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. Wall, C. R. ``On the Largest Odd Component of a Unitary Perfect Number.'' Fib. Quart. 25, 312-316, 1987.
- Projective Plane
- Projective Plane PK2
- Projective Space
- Projective Special Linear Group
- Projective Special Orthogonal Group
- Projective Special Unitary Group
- Projective Symplectic Group
- Projectivity
- Prolate Cycloid
- Prolate Cycloid Evolute
- Prolate Spheroid
- Prolate Spheroidal Coordinates
- Prolate Spheroidal Wave Function
- Pronic Number
- Proof
- Proofreading Mistakes
- Propeller
- Proper Cover
- Proper Divisor
- Proper Fraction
- Proper Integral
- Proper k-Coloring
- Proper Subset
- Proper Superset
- Proportional