Polyabolo
An analog of the Polyomino composed of 
Isosceles Right Triangles joined along edges of the same length. The number of polyaboloes composed of triangles are 1, 3, 4, 14, 30, 107,318, 1106, 3671, ... (Sloane's A006074).
References
Sloane, N. J. A. SequenceA006074/M2379in ``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.
- Nine-Point Center
- Nine-Point Circle
- Nine-Point Conic
- Nint
- Nint Zeta Function
- Nirenberg's Conjecture
- Niven Number
- Niven's Constant
- n-minex
- Nobbs Points
- Noble Number
- Node (Algebraic Curve)
- Node (Fixed Point)
- Node (Graph)
- Noetherian Module
- Noetherian Ring
- Noether-Lasker Theorem
- Noether's Fundamental Theorem
- Noether's Transformation Theorem
- Noise
- Noise Sphere
- Nolid
- Nome
- n-Omino
- Nomogram