I'm trying to identify this succulent I got from a friend. It spreads in two ways:
- Sometimes a stalk will tip to the side, and then sprout roots downward to creep along. One of the photos below documents this.
- More often, though, seeds form along the edge of the leaf, drop to the ground, and start new plants.

From my findings so far, the best I can figure is that it's some sort of kalanchoe - but I'm not entirely sure about that. 

Other info:
- Leaf parings alternate: one pair will be front and back, and the next will be left and right
- the leaf edges are serrated, and bear a thin red line along them
- I'm growing it inside, in a pot. It loves direct sunlight most of the day, and is thriving near windows
- I water it weekly, allowing it to completely dry between waterings. It seems quite happy with this arrangement.

[![the whole plant][1]][1]
[![leaf close up][2]][2]
[![the dropping and rooting behavior][3]][3]


  [1]: https://i.sstatic.net/ChmIL.jpg
  [2]: https://i.sstatic.net/z2rka.jpg
  [3]: https://i.sstatic.net/7l7pn.jpg