[57] For any nonnegative term series Σa_n, [0≦∃k＜1. ∃m∈N. ∀n∈N. n≧m ⇒ (n√a_n ≦ k ∨ a_{n+1}/a_n ≦ k)] ⇒ Σa_n converges.

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