x1[n] = {1,2,2,1,4}, y1[n]=x1[n]+y1[n-1]

Hello, im very new to this software and am having difficulty trying to write a script to derive and plot the above problem. I've entered the following code (written below) into the program but i'm not making any headway in geting the script I need, any of you guys able to point me in the right direction?

Much appreciated,

Ben

Code I've entered:

n=1
x[n]= {1 2 2 1 4}
y[n]=x1[n]+y1[n-1]
stem (n,y)