How can I evaluate the summation:
$\frac{1}{1^2+1}+\frac{1}{2^2+1}+\frac{1}{3^2+1}+\frac{1}{4^2+1}+\cdots$
I noticed that each term could be represented as $\dfrac{d(arctan(nx))}{(n)dx}=\dfrac{1}{n^2x^2+1}$
When $x=1$, the expression $\sum_{n=1}^{\infty}\dfrac{d(arctan(nx))}{ndx}$ becomes $\frac{1}{1^2+1}+\frac{1}{2^2+1}+\frac{1}{3^2+1}+\frac{1}{4^2+1}+\cdots$
However I cannot proceed any further. Is an exact value for the summation derivable?