Centered Triangular Number
A Centered Polygonal Number consisting of a central dot with three dots around it, and then additional dots in thegaps between adjacent dots. The general term is 
, and the first few such numbers are 1, 4, 10, 19, 31, 46,64, ... (Sloane's A005448). The Generating Function giving the centered triangular numbers is
See also Centered Pentagonal Number, Centered Square Number
References
Sloane, N. J. A. SequenceA005448/M3378in ``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.
- Class (Map)
- Class (Multiply Perfect Number)
- Class Number
- Class Number Formula
- Class Representative
- Class (Set)
- Clausen Formula
- Clausen Function
- Clausen's Integral
- CLEAN Algorithm
- CLEAN Beam
- CLEAN Map
- Clebsch-Aronhold Notation
- Clebsch Diagonal Cubic
- Clebsch-Gordan Coefficient
- Clement Matrix
- Clenshaw Recurrence Formula
- Clifford Algebra
- Clifford's Circle Theorem
- Clifford's Curve Theorem
- Cliff Random Number Generator
- Clique
- Clique Number
- Clock Solitaire
- Closed Curve