单词	triangular number
释义	triangular number noun : a number (such as 3, 6, 10, 15) representable by that many dots arranged in rows that form a triangle and that equals {latex}\\frac{n(n + 1)}{2}{/latex} for some positive integer value of n Word History First Known Use 1795, in the meaning defined above
随便看	the universe the unknown the unthinkable the unwashed the upper crust the upper hand the upshot the upstairs the usual the usual suspects the vanguard the Vatican The Villages the Virgin Mary the vote the walking wounded the warm the waterline the wave the wave of the future the way the way it goes the way it/life goes the way life goes the way of the world

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