Ah, the wonders of child development.
Two things to remember - at this age, he is developing quickly, which means growth spurts. These are not regular, but come in fits and starts. When the body is ready for him to grow, it will shut down by sending him into a deep sleep so it can concentrate all resources on growing his body cells. On the days when nothing much is happening on the development front, the body will direct his energy sources into using what he has, and exploring his ever changing world - hence lots of enery, and not much sleep required. There are no patterns for these developmental periods, they just occur when the body decides, and you have to work around them.
The other important thing is my own pet theory - that although we operate on a 24-hour cycle, biologically we operate on a 48-hour cycle. This means that even as adults, if we have an early night, it's not the day after we have loads of energy, it's the day after that, and the reverse is true for a short night's sleep. Your little one is already in this cycle now, so if you want him to be awake on Wednesday, put him down early on Monday.
It makes you wonder how the world got over-populated doesn't it!!! Little darlings!!!!!!!!!!!!!!!!!