50Hz OpAmp Multivibrator

Small component count multi-vibrator. Needed a clock of about 50 Hz (accuracy not critical). Mark/space is 1:1 and Period (T) = 2RC x log(e) ((R1 + 2R2)/R1) where, in this version, R=100k, C=330nF, R1=5k6, R2=1k. It'll need noise (a shake) to start.