A triangular number is a number that can form an equilateral triangle when represented as dots. The sequence starts with 1, 3, 6, 10, and continues by adding consecutive natural numbers. For example, the third triangular number is 6, which can be visualized as three rows of dots: one dot in the first row, two in the second, and three in the third. Triangular numbers can be calculated using the formula T_n = \fracn(n + 1)2 , where n is the position in the sequence. These numbers have applications in various fields, including mathematics, combinatorics, and number theory.