NISHIO Hirokazu[Translate]
三角数
T_n = \sum_{i=1}^n i = n(n + 1) / 2

三角数 - Wikipedia

Related Pages

"Engineer's way of creating knowledge" the English version of my book is now available on [Engineer's way of creating knowledge]
(C)NISHIO Hirokazu / Converted from [Scrapbox] at [Edit]