Let $$S_n=\sum_{k=1}^n\frac{n}{n^2+kn+k^2}$$ and $$T_n=\sum_{k=1}^n\frac{n-1}{n^2+kn+k^2} $$ for $n=1,2,3$. Then
- $S_n < π /3\sqrt{3}$
- $S_n > π/3\sqrt{3}$
- $T_n < π/3\sqrt{3}$
- $T_n> π/3\sqrt{3}$
Let $$S_n=\sum_{k=1}^n\frac{n}{n^2+kn+k^2}$$ and $$T_n=\sum_{k=1}^n\frac{n-1}{n^2+kn+k^2} $$ for $n=1,2,3$. Then