Differences between notch filter designs - use of op-amps
This configuration is called "Bootstrapped Twin T Filter". This filter is an active notch filter. A1 OpAmp is a simple voltage follower which will reduce output impedance. A2 is an another voltage follower used for the feedback. The usage of the voltage follower at the feedback is, it won't draw much current from the voltage divider feedback circuit and simply supply a feedback voltage to the filter. This will make the response is more oriented around our target frequency.

Texas instruments has a very good explanation about this design here. 

If you are going to use this design to build a circuit, I strongly suggest to use this. I have used this circuit to build a EEG circuit and had fabulous results!

Hope this helps :-)