Square triangular number
= Square triangular number
{wiki=Square_triangular_number}
A square triangular number is a number that is both a perfect square and a triangular number. A triangular number is a number that can be arranged in the shape of an equilateral triangle. The \\(n\\)-th triangular number is given by the formula: \\\[ T_n = \\frac\{n(n + 1)\}\{2\} \\\] where \\(n\\) is a positive integer. A perfect square is a number that can be expressed as the square of an integer.