# What's the chapter?

Algebra Level pending

If $$a_1, a_2,a_3,\ldots$$ follows a harmonic progression, and $$\displaystyle f(k) = \sum_{r=1}^n (a_r - a_k)$$, then $$\dfrac {a_1} {f(1)},\dfrac {a_2} {f(2)},\dfrac {a_3} {f(3)},\ldots, \dfrac {a_n} {f(n)}$$ follows a/an $$\text{__________}$$.

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