Correct Answer!

By the :

Consider the series

¥
å
n = 1 
| an| = ¥
å
n = 1 
arctan(n)
n2+1
and compare it to the convergent p-series (p=2) multiplied by a constant:

p
2
¥
å
n = 1 
1
n2
Since for n ³ 1

arctan(n)
n2+1
£ p/2
n2+1
£ p
2
æ
ç
è
1
n2
ö
÷
ø
then the implies convergence of the series.

Note that this problem can also be solved using the Integral Test and Limit Comparison Test.