Triangular number

Ten pebbles arranged into a triangle

A triangular number is a number that is the sum of all of the natural numbers up to a certain number. For example, 10 is a triangular number because 1 + 2 + 3 + 4 = 10. The first 25 triangular numbers are: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.

A triangular number is calculated by the equation: .

Other Languages
العربية: عدد مثلثي
azərbaycanca: Üçbucaq ədədləri
български: Триъгълно число
dansk: Trekanttal
Deutsch: Dreieckszahl
emiliàn e rumagnòl: Nùmer triangolèr
Esperanto: Triangula nombro
فارسی: عدد مثلثی
한국어: 삼각수
Bahasa Indonesia: Bilangan segitiga
Nederlands: Driehoeksgetal
日本語: 三角数
Nordfriisk: Triihuktaal
português: Número triangular
slovenščina: Trikotniško število
српски / srpski: Троугаони број
suomi: Kolmioluku
svenska: Triangeltal
українська: Трикутне число
Tiếng Việt: Số tam giác
中文: 三角形數