pds41: He handed over development after the first full release in 2011 with development passing on to Jens Bergensten only after the release.
So, I think my comment is correct; he got it out of beta and to a release stage pretty much on his own (very similar team size to Chris Sawyer's and Geoff Crammond's teams, being him, someone to do sounds, and then additional art and programming).
amok: No, because before 2011, Notch was not working on it by himself, 2011 was only when he passed on the lead developer role. Jeb was co-developer on Minecraft since late 2009. Minecraft had its first public beta in 2009, and the first release in 2011, so Jeb was co-creator since then. In the couple of years after the first release, they got a couple of more people in MOjang to work for it as well.
Okay, we're not going to agree. That's fine.
The 2011 team was four people, the same as the team size for Transport Tycoon, and the same as F1GP with similar role distribution (i.e. Notch = Sawyer = Geoff Crammond as the main programmer, with a person on each handling the sound, a person on each handling additional art and a person on each handling additional programming).
I'd also highlight that in my original post I did say "on the basis that small teams are allowed" and "pretty much on his own".