Answer: Well, yes. It's more like p = s + s + s + s. "S" = side. "P" = perimeter.
So, this is theoretically true if your variable for a side just happened to be "n".
You also put, "The perimeter of a square", A simpler way to put this is
P = s4 or in your case P = n4.
Because this shape is a square all side lengths and angles will be congruent, and therefore will all be the same (which is why we are able to multiply one side by four.)
Hope this helps. :)