What are all the triangle numbers up to 100?

Triangle numbers are generated by the formula ( T_n = \frac{n(n + 1)}{2} ). The triangle numbers up to 100 are: 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91. The largest triangle number less than or equal to 100 is 91.