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• ㉠ $\displaystyle \sum _ {n=1} ^ {\infty} \frac{\left (-1 \right) ^ {n+1} n} {n^2 +1}$ ㉡ $\displaystyle \sum _ {n=1} ^ {\infty} \frac{\sqrt n} {n^2 +1}$
• ㉢ $\displaystyle \sum _ {n=2} ^ {\infty} \frac{1} {n \ln n}$ ㉣ $\displaystyle \sum _ {n=1} ^ {\infty} \frac{n2^n} {4n^3 +1}$