Series Sums

Let S1 = 1 , S2 = 2 + 3, S3 = 4 + 5 + 6 ,........ Calculate S17.
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Let

$S_1 = 1$

$S_2 = 2 + 3$

$S_3 = 4 + 5 + 6$, $\cdots$


Calculate $S_{17}$