How the triangular pattern number works?

Answer 1

First, draw a dot. Below that, draw two dots. Then, 3 dots below it and so on.

Here, you should see the pattern of the triangular number, which is the sum of consecutive integers starting at 1. The terms of that pattern are 1, 3, 6, 10, 15, ....n(1 + n)/2 where n is the total number of dots for the pattern.