A centered triangular number is a centered polygonal number consisting of a central dot with three dots around it, and then additional dots in the gaps between adjacent dots. The th term is , and the first few such numbers for , 1, 2, ... are 1, 4, 10, 19, 31, 46, 64, ... (OEIS A005448). The generating function giving the centered triangular numbers is
Centered Triangular Number
See also
Centered Pentagonal Number, Centered Polygonal Number, Centered Square Number, Hex Number, Triangular NumberExplore with Wolfram|Alpha
References
Sloane, N. J. A. Sequence A005448/M3378 in "The On-Line Encyclopedia of Integer Sequences."Referenced on Wolfram|Alpha
Centered Triangular NumberCite this as:
Weisstein, Eric W. "Centered Triangular Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CenteredTriangularNumber.html