Prime Factors
The number of Distinct Prime Factors of a number 
is denoted 
. The first few values for 
,2, ... are 0, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, ... (Sloane's A001221; top figure). Thenumber of not necessarily distinct prime factors of a number is denoted 
. The first few values for ,2, ... are 0, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 2, 2, 4, 1, 3, 1, 3, ... (Sloane's A001222; bottom figure).
References
Sloane, N. J. A. SequencesA001222/M0094and A001221/M0056in ``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.
- Held Group
- Helen of Geometers
- Helicoid
- Helix
- Helly Number
- Helly's Theorem
- Helmholtz Differential Equation
- Helmholtz Differential Equation--Bipolar Coordinates
- Helmholtz Differential Equation--Cartesian Coordinates
- Helmholtz Differential Equation--Circular Cylindrical Coordinates
- Helmholtz Differential Equation--Confocal Ellipsoidal Coordinates
- Helmholtz Differential Equation--Confocal Paraboloidal Coordinates
- Helmholtz Differential Equation--Conical Coordinates
- Helmholtz Differential Equation--Elliptic Cylindrical Coordinates
- Helmholtz Differential Equation--Oblate Spheroidal Coordinates
- Helmholtz Differential Equation--Parabolic Coordinates
- Helmholtz Differential Equation--Parabolic Cylindrical Coordinates
- Helmholtz Differential Equation Polar Coordinates
- Helmholtz Differential Equation--Prolate Spheroidal Coordinates
- Helmholtz Differential Equation--Spherical Coordinates
- Helmholtz Differential Equation--Spherical Surface
- Helmholtz Differential Equation--Toroidal Coordinates
- Helmholtz's Theorem
- Helson-Szegö Measure
- Hemicylindrical Function