On the TI Nspire, plotting of graph with discrete values sometimes do not easily give desired results. Consider plotting
Using 2D graph, Nspire will actually plot the graph but is seemingly having problems connecting the points. Not only after the integer function is added into the equation, the graph can be visualized properly. Experimenting with the Trace function below, the red trace disappears on real X values between two discrete integers, confirming the plot is there but the engine is having problem connecting.
In contrast, the HP Prime provided an Integer view of graph for this case.