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For which positive integers n is the rat...

For which positive integers `n` is the ratio, `(sum+(k=1)^(n) k^(2))/(sum_(k=1)^(n) k)` an integer ?

A

odd `n` only

B

even `n` only

C

`n = 1 + 6k` only, where `k ge 0 and k in 1`

D

`n = 1 + 3k, " integer " k ge 0`

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The correct Answer is:
D
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