287

Number
$287$ (two hundred and eighty-seven) is:


 * $7 \times 41$


 * The $14$th pentagonal number after $1, 5, 12, 22, 35, 51, 70, 92, 117, 145, 176, 210, 247$:
 * $287 = \displaystyle \sum_{k \mathop = 1}^{14} \left({3 k - 2}\right) = \dfrac {14 \left({3 \times 14 - 1}\right)} 2$


 * The $27$th generalized pentagonal number after $1, 2, 5, 7, 12, 15, \ldots, 126, 145, 176, 187, 210, 222, 247, 260$:
 * $287 = \dfrac {14 \left({3 \times 14 - 1}\right)} 2$