D-Number
A Natural Number 
such that
whenever
(
and 
are Relatively Prime) and 
. There are an infinite number of such numbers,the first few being 9, 15, 21, 33, 39, 51, ... (Sloane's A033553).See also Knödel Numbers
References
Makowski, A. ``Generalization of Morrow's 
-Numbers.'' Simon Stevin 36, 71, 1962/1963.
Sloane, N. J. A. Sequence A033553in ``The On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html.
- Argument Addition Relation
- Argument (Complex Number)
- Argument (Elliptic Integral)
- Argument (Function)
- Argument Multiplication Relation
- Argument Principle
- Argument Variation
- Aristotle's Wheel Paradox
- Arithmetic
- Arithmetic-Geometric Mean
- Arithmetic Geometry
- Arithmetic-Harmonic Mean
- Arithmetic-Logarithmic-Geometric Mean Inequality
- Arithmetic Mean
- Arithmetic Progression
- Arithmetic Sequence
- Arithmetic Series
- Armstrong Number
- Arnold Diffusion
- Arnold's Cat Map
- Arnold Tongue
- Aronhold Process
- Aronson's Sequence
- Arrangement
- Arrangement Number