Figurate number that can be represented by sets of points arranged on the edges of a regular tetrahedron or by a sequence that is partially interlocked with regular tetrahedrons.
- The sequence of pyramidal numbers is: 1, 4, 10, 20, …, \(\dfrac{1}{6}\)n (n + 1)(n + 2) where n corresponds to the number of points on an edge of the pyramid.
- The pyramidal numbers are also called tetrahedral numbers.