What is the 18th triangular number?

Answer 1

The 18th triangular number is calculated using the formula ( T_n = \frac{n(n + 1)}{2} ), where ( n ) is the position in the sequence. For ( n = 18 ), this gives ( T_{18} = \frac{18 \times 19}{2} = 171 ). Therefore, the 18th triangular number is 171.