You don't need a closed form expression to graph the function. In order to graph the function, you would have to evaluate the function at various values of n, which you can easily do with the recursive definition.

To get an idea what the closed form expression would look like, we can start by assuming the first term is 1. We will then get the sequence 1, 3, 11, 123, 15132 and so on. At this point, the +2 is negligible and you would get an expression that is approximately something to the power of 2^x.