1717
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Number
$1717$ (one thousand, seven hundred and seventeen) is:
- $17 \times 101$
- The $34$th pentagonal number after $1$, $5$, $12$, $22$, $35$, $\ldots$, $925$, $1001$, $1080$, $1162$, $1247$, $1335$, $1426$, $1520$, $1617$:
- $1717 = \ds \sum_{k \mathop = 1}^{34} \paren {3 k - 2} = \dfrac {34 \paren {3 \times 34 - 1} } 2$
- The $67$th generalized pentagonal number after $1$, $2$, $5$, $7$, $12$, $15$, $\ldots$, $1335$, $1365$, $1426$, $1457$, $1520$, $1552$, $1617$, $1650$:
- $1717 = \ds \sum_{k \mathop = 1}^{34} \paren {3 k - 2} = \dfrac {34 \paren {3 \times 34 - 1} } 2$