∑k = (n(n+1)/2)

1

∑k = (n(n+1)/2)

2

∑k = (n(n+1)/2)

3

∑k = (n(n+1)/2)

4

∑k = (n(n+1)/2)

5

∑k = (n(n+1)/2)

6

∑k = (n(n+1)/2)

7

∑k = (n(n+1)/2)

8

∑k = (n(n+1)/2)

9

∑k = (n(n+1)/2)

10

∑k = (n(n+1)/2)

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