Triangular numbers are introduced in this video which shows how triangular numbers are found and then proceeds to explain Gauss' method for adding arithmetic sequences.

Continuing the podcast from Triangular Numbers (Part I), the Gaussian formula for summing numbers of an arithmetic sequence is derived with good explanation, and then used for a couple examples.

Continuing from Triangular Numbers (Part II), the podcast solves Gauss' formula for the sum of an arithmetic sequence. Recursive equations are explained heavily, and used in order to solve the Gauss formula.