Octahedral Number
Given a number n, the task is to find n-th octahedral number. An octahedral number belongs to a figurate number and it is the number of spheres in an octahedron built from closely packed spheres. First, a few octahedral numbers (where n = 0, 1, 2, 3â¦â¦.) are 0, 1, 6, 19, and so on. Examples : Input: