Editing Triangular number (section)

{{Short description|Figurate number}}
[[File:First six triangular numbers.svg|thumb|The first six triangular numbers (not starting with ''T''<sub>0</sub>, but rather, ''T''<sub>1</sub>)]]
[[File:Triangular Numbers Plot.svg|thumb|Triangular Numbers Plot]]
A '''triangular number''' or '''triangle number''' counts objects arranged in an [[equilateral triangle]]. Triangular numbers are a type of [[figurate number]], other examples being [[square number]]s and [[Cube (algebra)#In integers|cube numbers]]. The {{mvar|n}}th triangular number is the number of dots in the triangular arrangement with {{mvar|n}} dots on each side, and is equal to the sum of the {{mvar|n}} [[natural number]]s from 1 to {{mvar|n}}. The first 100 terms [[Integer sequence|sequence]] of triangular numbers, starting with the [[Empty sum|0th triangular number]], are
{{block indent|left=1.6|0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630, 666, 703, 741, 780, 820, 861, 903, 946, 990, 1035, 1081, 1128, 1176, 1225, 1275, 1326, 1378, 1431, 1485, 1540, 1596, 1653, 1711, 1770, 1830, 1891, 1953, 2016, 2080, 2145, 2211, 2278, 2346, 2415, 2485, 2556, 2628, 2701, 2775, 2850, 2926, 3003, 3081, 3160, 3240, 3321, 3403, 3486, 3570, 3655, 3741, 3828, 3916, 4005, 4095, 4186, 4278, 4371, 4465, 4560, 4656, 4753, 4851, 4950, 5050...}}
{{OEIS|id=A000217}}