Discovering relationships and patterns by exploring trapezoidal numbers
Paul W. Haggard, Kelly L. Morales · International Journal of Mathematical Education in Science and Technology · 1993
The trapezoidal numbers are defined from the well known triangular numbers. A discovery type approach is used to find properties of these numbers. At times, geometry provides a property but most properties are observed from a table of the numbers. Patterns are given that identify several types of polygonal numbers in the table of trapezoidal numbers.