An A319 First Officer reported fatigue induced errors as a result of inadequate rest on a four day scheduled flight sequence. The assignment included an 'all nighter' in the middle; which required circadian rhythm adaptation twice in the four days.

Narrative

My most recent scheduled flight sequence is not safe. There is a red eye in the middle of a four day sequence. As a result; it is impossible to get proper rest. I had two nights of sleep and two short naps in 4 days on this trip.On the last day; I was missing radio calls and forgetting if I accomplished required tasks. On final on the last leg; I forgot to select an ILS back-up for a visual approach. I was missing many tasks which are normal for my habit patterns. Any one of the many issues that I experienced on the last day (3 legs) of the flight sequence were minor; but taken in whole I now realize how tired I was. The worrisome part of this is that I did not realize it at the time.I do not think it is possible to safely change your circadian rhythm by 12 hours twice in 4 days. I had 4 different Captains on this trip; so none of them experienced fatigue like me. I had flown with one of the Captains before and he noticed and mentioned how tired I looked and that I was not my normal self. These types of trips should not be scheduled. Legal is not always safe.