11 statements · 18% with external sources · numbers in brackets are citations
\Delta_n = \binom{n+1}{2} = \frac{n (n + 1)}{2}, n \ge 1 \Delta_n symbol represents: triangular numbern symbol represents: positive integer7 identifiers linking triangular number across the web's reference databases
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The triangular numbers or triangle numbers are the sequence of positive integers that can be represented as a lattice of points arranged in an equilateral triangle. The triangular lattice representing the th triangular number contains rows: the first row contains one point, the second row contains two, and this pattern continues up to the th row, which contains . Therefore, the triangular numbers may also be represented by the formula.