385614domain: NAppears in sequencesa(n) = 729*n^2 - 27.at n=22A158655Number of polygon edges formed when every pair of vertices of a regular n-gon are joined by an infinite line.at n=36A344899Number of polygon edges formed when every pair of vertices of a regular (2n-1)-gon are joined by an infinite line.at n=18A344907