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出典:Wiktionary
出典:『Wiktionary』 (2026/04/03 00:04 UTC 版)
triangular number (plural triangular numbers)
出典:Wikipedia
出典:『Wikipedia』 (2011/07/25 03:47 UTC 版)
A triangular number or triangle number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangle number. The nth triangle number is the number of dots in a triangle with n dots on a side.
triangular number