Sum this infinite series: sum[-infty,+infty] 1/(n^2+n+1) (w/ tan(h) appearing)

[Jingtingbai]

Can anyone help me with summing this infinite series:

. . . . .$\displaystyle \displaystyle \sum_{-\infty}^{\infty}\, \dfrac{1}{n^2\, +\, n\, +\, 1}$

with the function tan(h) appearing as a major factor in the result? Thanks a lot!