Almost like a star shape but with the points rounded off. I used this node setup to make a star like this, but I can't figure out how to round off the edges. I would like to be able to customize the number of bumps.
After some quick experimenting, I actually figured out how to get this outcome. If you put an rgb curves node after the ping-pong node (I also got rid of the add and divide nodes because i realised that they weren't necessary) and give the rgb curve a u shape, you can get this outcome. The less than node controls the size and changing the height of the u shape changes the height of the bumps