Ideal (Partial Order)
An ideal 
of a Partial Order 
is a subset of the elements of which satisfy the property thatif 
and 
, then 
. For 
disjoint chains in which the 
th chain contains 
elements,there are 
ideals. The number of ideals of a 
-element Fence Poset is theFibonacci Number 
.
References
Ruskey, F. ``Information on Ideals of Partially Ordered Sets.'' http://sue.csc.uvic.ca/~cos/inf/pose/Ideals.html. Steiner, G. ``An Algorithm to Generate the Ideals of a Partial Order.'' Operat. Res. Let. 5, 317-320, 1986.
- Elliptic Logarithm
- Elliptic Modular Function
- Elliptic Paraboloid
- Elliptic Partial Differential Equation
- Elliptic Plane
- Elliptic Point
- Elliptic Pseudoprime
- Elliptic Rotation
- Elliptic Theta Function
- Elliptic Torus
- Elliptic Umbilic Catastrophe
- Ellison-Mendès-France Constant
- Elongated Cupola
- Elongated Dipyramid
- Elongated Dodecahedron
- Elongated Gyrobicupola
- Elongated Gyrocupolarotunda
- Elongated Orthobicupola
- Elongated Orthobirotunda
- Elongated Orthocupolarotunda
- Elongated Pentagonal Cupola
- Elongated Pentagonal Dipyramid
- Elongated Pentagonal Gyrobicupola
- Elongated Pentagonal Gyrobirotunda
- Elongated Pentagonal Gyrocupolarotunda