A centered polygonal number consisting of a central dot with five dots around it, and then additional dots in the gaps between adjacent dots. The general term is , and the first few such numbers are 1, 6, 16, 31, 51, 76, ... (OEIS A005891). The generating function of the centered pentagonal numbers is
Centered Pentagonal Number
See also
Centered Polygonal Number, Centered Square Number, Centered Triangular Number, Hex Number, Pentagonal NumberExplore with Wolfram|Alpha
References
Sloane, N. J. A. Sequence A005891/M4112 in "The On-Line Encyclopedia of Integer Sequences."Referenced on Wolfram|Alpha
Centered Pentagonal NumberCite this as:
Weisstein, Eric W. "Centered Pentagonal Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CenteredPentagonalNumber.html